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	$27.61	4.505%	$28.8538	$28.85	$28.85	$28.90
Purchase #2	$146.86	8.443%	$159.2594	$159.26	$159.25	$159.30
Purchase #3	$106.30	4.841%	$111.446	$111.45	$111.45	$111.40
Purchase #4	$73.48	11.166%	$81.6848	$81.68	$81.70	$81.70
Purchase #5	$169.72	9.480%	$185.8095	$185.81	$185.80	$185.80
Purchase #6	$18.35	13.673%	$20.859	$20.86	$20.85	$20.90
Purchase #7	$110.59	10.530%	$122.2351	$122.24	$122.25	$122.20
7 purchase totals =	$652.91		$710.1476	$710.15	$710.15	$710.20