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	$95.65	4.391%	$99.85	$99.85	$99.85	$99.90
Purchase #2	$250.48	8.867%	$272.6901	$272.69	$272.70	$272.70
Purchase #3	$131.31	7.462%	$141.1084	$141.11	$141.10	$141.10
Purchase #4	$149.88	10.750%	$165.9921	$165.99	$166.00	$166.00
Purchase #5	$246.73	3.488%	$255.3359	$255.34	$255.35	$255.30
Purchase #6	$93.57	6.255%	$99.4228	$99.42	$99.40	$99.40
Purchase #7	$160.89	13.829%	$183.1395	$183.14	$183.15	$183.10
7 purchase totals =	$1,128.51		$1,217.5388	$1,217.54	$1,217.55	$1,217.50