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	$234.43	7.455%	$251.9068	$251.91	$251.90	$251.90
Purchase #2	$173.98	13.130%	$196.8236	$196.82	$196.80	$196.80
Purchase #3	$108.73	4.145%	$113.2369	$113.24	$113.25	$113.20
Purchase #4	$244.55	13.489%	$277.5373	$277.54	$277.55	$277.50
Purchase #5	$111.85	11.351%	$124.5461	$124.55	$124.55	$124.50
Purchase #6	$116.37	5.404%	$122.6586	$122.66	$122.65	$122.70
Purchase #7	$136.55	4.393%	$142.5486	$142.55	$142.55	$142.50
7 purchase totals =	$1,126.46		$1,229.2579	$1,229.27	$1,229.25	$1,229.10