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	$159.86	3.269%	$165.0858	$165.09	$165.10	$165.10
Purchase #2	$92.86	3.358%	$95.9782	$95.98	$96.00	$96.00
Purchase #3	$130.73	3.105%	$134.7892	$134.79	$134.80	$134.80
Purchase #4	$101.42	9.778%	$111.3368	$111.34	$111.35	$111.30
Purchase #5	$211.45	5.519%	$223.1199	$223.12	$223.10	$223.10
Purchase #6	$196.74	3.382%	$203.3937	$203.39	$203.40	$203.40
Purchase #7	$149.81	11.240%	$166.6486	$166.65	$166.65	$166.60
7 purchase totals =	$1,042.87		$1,100.3522	$1,100.36	$1,100.40	$1,100.30