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	$248.90	10.597%	$275.2759	$275.28	$275.30	$275.30
Purchase #2	$241.68	7.316%	$259.3613	$259.36	$259.35	$259.40
Purchase #3	$78.56	3.442%	$81.264	$81.26	$81.25	$81.30
Purchase #4	$174.83	10.356%	$192.9354	$192.94	$192.95	$192.90
Purchase #5	$5.76	4.542%	$6.0216	$6.02	$6.00	$6.00
Purchase #6	$175.57	5.425%	$185.0947	$185.09	$185.10	$185.10
Purchase #7	$98.47	13.537%	$111.7999	$111.80	$111.80	$111.80
7 purchase totals =	$1,023.77		$1,111.7528	$1,111.75	$1,111.75	$1,111.80