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	4.789%	$53.0547	$53.05	$53.05	$53.10
Purchase #2	$232.46	3.485%	$240.5612	$240.56	$240.55	$240.60
Purchase #3	$26.65	5.738%	$28.1792	$28.18	$28.20	$28.20
Purchase #4	$237.51	7.614%	$255.594	$255.59	$255.60	$255.60
Purchase #5	$137.45	6.139%	$145.8881	$145.89	$145.90	$145.90
Purchase #6	$149.33	11.270%	$166.1595	$166.16	$166.15	$166.20
Purchase #7	$54.51	6.805%	$58.2194	$58.22	$58.20	$58.20
7 purchase totals =	$888.54		$947.6561	$947.65	$947.65	$947.80