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	$50.56	8.396%	$54.805	$54.81	$54.80	$54.80
Purchase #2	$52.56	9.553%	$57.5811	$57.58	$57.60	$57.60
Purchase #3	$122.30	6.556%	$130.318	$130.32	$130.30	$130.30
Purchase #4	$60.35	12.215%	$67.7218	$67.72	$67.70	$67.70
Purchase #5	$113.77	13.228%	$128.8195	$128.82	$128.80	$128.80
Purchase #6	$68.95	3.199%	$71.1557	$71.16	$71.15	$71.20
Purchase #7	$235.48	3.183%	$242.9753	$242.98	$243.00	$243.00
7 purchase totals =	$703.97		$753.3764	$753.39	$753.35	$753.40