Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$156.49	6.613%	$166.8387	$166.84	$166.85	$166.80
Purchase #2	$52.71	12.292%	$59.1891	$59.19	$59.20	$59.20
Purchase #3	$43.64	6.600%	$46.5202	$46.52	$46.50	$46.50
Purchase #4	$42.87	12.381%	$48.1777	$48.18	$48.20	$48.20
Purchase #5	$190.59	9.793%	$209.2545	$209.25	$209.25	$209.30
Purchase #6	$250.77	11.595%	$279.8468	$279.85	$279.85	$279.80
Purchase #7	$232.25	7.146%	$248.8466	$248.85	$248.85	$248.80
7 purchase totals =	$969.32		$1,058.6736	$1,058.68	$1,058.70	$1,058.60