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	$178.52	11.318%	$198.7249	$198.72	$198.70	$198.70
Purchase #2	$135.95	9.261%	$148.5403	$148.54	$148.55	$148.50
Purchase #3	$70.46	11.602%	$78.6348	$78.63	$78.65	$78.60
Purchase #4	$40.31	8.310%	$43.6598	$43.66	$43.65	$43.70
Purchase #5	$219.54	8.699%	$238.6378	$238.64	$238.65	$238.60
Purchase #6	$137.84	8.698%	$149.8293	$149.83	$149.85	$149.80
Purchase #7	$126.87	13.625%	$144.156	$144.16	$144.15	$144.20
7 purchase totals =	$909.49		$1,002.1829	$1,002.18	$1,002.20	$1,002.10