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	$54.77	8.709%	$59.5399	$59.54	$59.55	$59.50
Purchase #2	$196.97	7.170%	$211.0927	$211.09	$211.10	$211.10
Purchase #3	$10.51	13.124%	$11.8893	$11.89	$11.90	$11.90
Purchase #4	$143.52	5.661%	$151.6447	$151.64	$151.65	$151.60
Purchase #5	$28.74	11.867%	$32.1506	$32.15	$32.15	$32.20
Purchase #6	$27.37	3.556%	$28.3433	$28.34	$28.35	$28.30
Purchase #7	$224.72	12.163%	$252.0527	$252.05	$252.05	$252.10
7 purchase totals =	$686.60		$746.7132	$746.70	$746.75	$746.70