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	$9.44	8.869%	$10.2772	$10.28	$10.30	$10.30
Purchase #2	$125.72	11.364%	$140.0068	$140.01	$140.00	$140.00
Purchase #3	$222.89	13.315%	$252.5678	$252.57	$252.55	$252.60
Purchase #4	$128.29	3.421%	$132.6788	$132.68	$132.70	$132.70
Purchase #5	$105.83	5.185%	$111.3173	$111.32	$111.30	$111.30
Purchase #6	$247.98	3.601%	$256.9098	$256.91	$256.90	$256.90
Purchase #7	$237.32	6.802%	$253.4625	$253.46	$253.45	$253.50
7 purchase totals =	$1,077.47		$1,157.2202	$1,157.23	$1,157.20	$1,157.30