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	$70.29	3.314%	$72.6194	$72.62	$72.60	$72.60
Purchase #2	$48.81	5.597%	$51.5419	$51.54	$51.55	$51.50
Purchase #3	$238.69	9.415%	$261.1627	$261.16	$261.15	$261.20
Purchase #4	$152.51	4.862%	$159.925	$159.93	$159.95	$159.90
Purchase #5	$59.26	5.568%	$62.5596	$62.56	$62.55	$62.60
Purchase #6	$5.33	3.556%	$5.5195	$5.52	$5.50	$5.50
Purchase #7	$157.50	5.640%	$166.383	$166.38	$166.40	$166.40
7 purchase totals =	$732.39		$779.7111	$779.71	$779.70	$779.70