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	$111.34	12.606%	$125.3755	$125.38	$125.40	$125.40
Purchase #2	$82.82	13.633%	$94.1109	$94.11	$94.10	$94.10
Purchase #3	$143.77	12.625%	$161.921	$161.92	$161.90	$161.90
Purchase #4	$156.50	10.506%	$172.9419	$172.94	$172.95	$172.90
Purchase #5	$222.82	13.657%	$253.2505	$253.25	$253.25	$253.30
Purchase #6	$111.75	11.833%	$124.9734	$124.97	$124.95	$125.00
Purchase #7	$145.54	6.321%	$154.7396	$154.74	$154.75	$154.70
7 purchase totals =	$974.54		$1,087.3128	$1,087.31	$1,087.30	$1,087.30