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	$117.72	9.343%	$128.7186	$128.72	$128.70	$128.70
Purchase #2	$134.77	12.759%	$151.9653	$151.97	$151.95	$152.00
Purchase #3	$116.63	10.511%	$128.889	$128.89	$128.90	$128.90
Purchase #4	$78.77	9.386%	$86.1634	$86.16	$86.15	$86.20
Purchase #5	$243.98	12.538%	$274.5702	$274.57	$274.55	$274.60
Purchase #6	$26.45	13.802%	$30.1006	$30.10	$30.10	$30.10
Purchase #7	$250.52	4.168%	$260.9617	$260.96	$260.95	$261.00
7 purchase totals =	$968.84		$1,061.3688	$1,061.37	$1,061.30	$1,061.50