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	$148.54	9.494%	$162.6424	$162.64	$162.65	$162.60
Purchase #2	$166.98	12.693%	$188.1748	$188.17	$188.15	$188.20
Purchase #3	$171.56	9.664%	$188.1396	$188.14	$188.15	$188.10
Purchase #4	$33.57	4.700%	$35.1478	$35.15	$35.15	$35.10
Purchase #5	$15.96	12.582%	$17.9681	$17.97	$17.95	$18.00
Purchase #6	$40.91	10.266%	$45.1098	$45.11	$45.10	$45.10
Purchase #7	$35.96	6.655%	$38.3531	$38.35	$38.35	$38.40
7 purchase totals =	$613.48		$675.5356	$675.53	$675.50	$675.50