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	$112.68	5.129%	$118.4594	$118.46	$118.45	$118.50
Purchase #2	$111.39	11.485%	$124.1831	$124.18	$124.20	$124.20
Purchase #3	$100.42	11.347%	$111.8147	$111.81	$111.80	$111.80
Purchase #4	$138.40	6.672%	$147.634	$147.63	$147.65	$147.60
Purchase #5	$132.55	4.347%	$138.3119	$138.31	$138.30	$138.30
Purchase #6	$37.82	10.799%	$41.9042	$41.90	$41.90	$41.90
Purchase #7	$36.38	9.726%	$39.9183	$39.92	$39.90	$39.90
7 purchase totals =	$669.64		$722.2256	$722.21	$722.20	$722.20