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	$144.48	10.109%	$159.0855	$159.09	$159.10	$159.10
Purchase #2	$148.89	8.547%	$161.6156	$161.62	$161.60	$161.60
Purchase #3	$157.42	6.239%	$167.2414	$167.24	$167.25	$167.20
Purchase #4	$30.63	3.758%	$31.7811	$31.78	$31.80	$31.80
Purchase #5	$110.77	11.371%	$123.3657	$123.37	$123.35	$123.40
Purchase #6	$89.35	11.848%	$99.9362	$99.94	$99.95	$99.90
Purchase #7	$246.26	7.479%	$264.6778	$264.68	$264.70	$264.70
7 purchase totals =	$927.80		$1,007.7033	$1,007.72	$1,007.75	$1,007.70