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	$147.80	5.467%	$155.8802	$155.88	$155.90	$155.90
Purchase #2	$84.82	11.584%	$94.6455	$94.65	$94.65	$94.60
Purchase #3	$229.28	5.805%	$242.5897	$242.59	$242.60	$242.60
Purchase #4	$200.53	10.631%	$221.8483	$221.85	$221.85	$221.80
Purchase #5	$230.35	11.457%	$256.7412	$256.74	$256.75	$256.70
Purchase #6	$148.80	11.785%	$166.3361	$166.34	$166.35	$166.30
Purchase #7	$31.89	7.482%	$34.276	$34.28	$34.30	$34.30
7 purchase totals =	$1,073.47		$1,172.3170	$1,172.33	$1,172.40	$1,172.20