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	$64.66	9.355%	$70.7089	$70.71	$70.70	$70.70
Purchase #2	$127.30	13.328%	$144.2665	$144.27	$144.25	$144.30
Purchase #3	$65.68	6.808%	$70.1515	$70.15	$70.15	$70.20
Purchase #4	$118.51	4.822%	$124.2246	$124.22	$124.20	$124.20
Purchase #5	$133.44	9.533%	$146.1608	$146.16	$146.15	$146.20
Purchase #6	$43.27	6.218%	$45.9605	$45.96	$45.95	$46.00
Purchase #7	$59.27	4.464%	$61.9158	$61.92	$61.90	$61.90
7 purchase totals =	$612.13		$663.3886	$663.39	$663.30	$663.50