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	$221.68	13.142%	$250.8132	$250.81	$250.80	$250.80
Purchase #2	$131.69	6.127%	$139.7586	$139.76	$139.75	$139.80
Purchase #3	$98.82	13.186%	$111.8504	$111.85	$111.85	$111.90
Purchase #4	$109.34	6.199%	$116.118	$116.12	$116.10	$116.10
Purchase #5	$61.33	6.513%	$65.3244	$65.32	$65.30	$65.30
Purchase #6	$241.77	12.844%	$272.8229	$272.82	$272.80	$272.80
Purchase #7	$247.35	5.344%	$260.5684	$260.57	$260.55	$260.60
7 purchase totals =	$1,111.98		$1,217.2559	$1,217.25	$1,217.15	$1,217.30