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	$166.68	9.290%	$182.1646	$182.16	$182.15	$182.20
Purchase #2	$34.63	3.814%	$35.9508	$35.95	$35.95	$36.00
Purchase #3	$129.38	10.641%	$143.1473	$143.15	$143.15	$143.10
Purchase #4	$155.90	10.554%	$172.3537	$172.35	$172.35	$172.40
Purchase #5	$76.89	8.775%	$83.6371	$83.64	$83.65	$83.60
Purchase #6	$82.97	11.427%	$92.451	$92.45	$92.45	$92.50
Purchase #7	$40.98	6.734%	$43.7396	$43.74	$43.75	$43.70
7 purchase totals =	$687.43		$753.4441	$753.44	$753.45	$753.50