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	$125.70	13.817%	$143.068	$143.07	$143.05	$143.10
Purchase #2	$204.76	3.281%	$211.4782	$211.48	$211.50	$211.50
Purchase #3	$33.48	12.237%	$37.5769	$37.58	$37.60	$37.60
Purchase #4	$163.32	5.809%	$172.8073	$172.81	$172.80	$172.80
Purchase #5	$91.44	4.740%	$95.7743	$95.77	$95.75	$95.80
Purchase #6	$240.36	6.489%	$255.957	$255.96	$255.95	$256.00
Purchase #7	$118.89	7.811%	$128.1765	$128.18	$128.20	$128.20
7 purchase totals =	$977.95		$1,044.8382	$1,044.85	$1,044.85	$1,045.00