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	$50.63	8.221%	$54.7923	$54.79	$54.80	$54.80
Purchase #2	$77.85	7.466%	$83.6623	$83.66	$83.65	$83.70
Purchase #3	$212.29	7.317%	$227.8233	$227.82	$227.80	$227.80
Purchase #4	$172.33	3.873%	$179.0043	$179.00	$179.00	$179.00
Purchase #5	$233.92	4.409%	$244.2335	$244.23	$244.25	$244.20
Purchase #6	$223.82	5.345%	$235.7832	$235.78	$235.80	$235.80
Purchase #7	$36.87	13.523%	$41.8559	$41.86	$41.85	$41.90
7 purchase totals =	$1,007.71		$1,067.1548	$1,067.14	$1,067.15	$1,067.20