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	$59.82	5.555%	$63.143	$63.14	$63.15	$63.10
Purchase #2	$157.32	9.460%	$172.2025	$172.20	$172.20	$172.20
Purchase #3	$247.78	8.774%	$269.5202	$269.52	$269.50	$269.50
Purchase #4	$173.28	13.549%	$196.7577	$196.76	$196.75	$196.80
Purchase #5	$32.64	10.195%	$35.9676	$35.97	$35.95	$36.00
Purchase #6	$169.42	13.399%	$192.1206	$192.12	$192.10	$192.10
Purchase #7	$29.63	9.695%	$32.5026	$32.50	$32.50	$32.50
7 purchase totals =	$869.89		$962.2142	$962.21	$962.15	$962.20