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	$156.37	5.693%	$165.2721	$165.27	$165.25	$165.30
Purchase #2	$69.35	13.834%	$78.9439	$78.94	$78.95	$78.90
Purchase #3	$55.45	12.184%	$62.206	$62.21	$62.20	$62.20
Purchase #4	$40.98	11.680%	$45.7665	$45.77	$45.75	$45.80
Purchase #5	$96.69	6.694%	$103.1624	$103.16	$103.15	$103.20
Purchase #6	$161.89	7.612%	$174.2131	$174.21	$174.20	$174.20
Purchase #7	$98.41	12.762%	$110.9691	$110.97	$110.95	$111.00
7 purchase totals =	$679.14		$740.5331	$740.53	$740.45	$740.60