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	$46.56	8.778%	$50.647	$50.65	$50.65	$50.60
Purchase #2	$108.80	3.733%	$112.8615	$112.86	$112.85	$112.90
Purchase #3	$199.54	5.403%	$210.3211	$210.32	$210.30	$210.30
Purchase #4	$89.68	6.731%	$95.7164	$95.72	$95.70	$95.70
Purchase #5	$175.98	11.733%	$196.6277	$196.63	$196.65	$196.60
Purchase #6	$63.72	6.470%	$67.8427	$67.84	$67.85	$67.80
Purchase #7	$203.28	3.670%	$210.7404	$210.74	$210.75	$210.70
7 purchase totals =	$887.56		$944.7568	$944.76	$944.75	$944.60