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	$108.89	13.279%	$123.3495	$123.35	$123.35	$123.30
Purchase #2	$134.63	9.166%	$146.9702	$146.97	$146.95	$147.00
Purchase #3	$99.46	4.211%	$103.6483	$103.65	$103.65	$103.60
Purchase #4	$149.77	11.428%	$166.8857	$166.89	$166.90	$166.90
Purchase #5	$159.39	8.319%	$172.6497	$172.65	$172.65	$172.60
Purchase #6	$154.84	13.838%	$176.2668	$176.27	$176.25	$176.30
Purchase #7	$161.98	10.246%	$178.5765	$178.58	$178.60	$178.60
7 purchase totals =	$968.96		$1,068.3467	$1,068.36	$1,068.35	$1,068.30