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	$66.61	8.348%	$72.1706	$72.17	$72.15	$72.20
Purchase #2	$152.29	13.164%	$172.3375	$172.34	$172.35	$172.30
Purchase #3	$101.29	4.592%	$105.9412	$105.94	$105.95	$105.90
Purchase #4	$79.69	13.633%	$90.5541	$90.55	$90.55	$90.60
Purchase #5	$170.68	10.150%	$188.004	$188.00	$188.00	$188.00
Purchase #6	$161.30	8.637%	$175.2315	$175.23	$175.25	$175.20
Purchase #7	$194.52	13.448%	$220.679	$220.68	$220.70	$220.70
7 purchase totals =	$926.38		$1,024.9179	$1,024.91	$1,024.95	$1,024.90