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	$123.77	3.147%	$127.665	$127.67	$127.65	$127.70
Purchase #2	$89.53	7.151%	$95.9323	$95.93	$95.95	$95.90
Purchase #3	$87.80	3.591%	$90.9529	$90.95	$90.95	$91.00
Purchase #4	$134.29	10.481%	$148.3649	$148.36	$148.35	$148.40
Purchase #5	$144.97	9.512%	$158.7595	$158.76	$158.75	$158.80
Purchase #6	$28.82	11.408%	$32.1078	$32.11	$32.10	$32.10
Purchase #7	$201.42	7.584%	$216.6957	$216.70	$216.70	$216.70
7 purchase totals =	$810.60		$870.4781	$870.48	$870.45	$870.60