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	$216.67	12.547%	$243.8556	$243.86	$243.85	$243.90
Purchase #2	$42.99	8.696%	$46.7284	$46.73	$46.75	$46.70
Purchase #3	$36.38	4.820%	$38.1335	$38.13	$38.15	$38.10
Purchase #4	$81.61	9.253%	$89.1614	$89.16	$89.15	$89.20
Purchase #5	$147.88	9.462%	$161.8724	$161.87	$161.85	$161.90
Purchase #6	$30.30	5.846%	$32.0713	$32.07	$32.05	$32.10
Purchase #7	$18.69	4.113%	$19.4587	$19.46	$19.45	$19.50
7 purchase totals =	$574.52		$631.2813	$631.28	$631.25	$631.40