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	$152.62	12.622%	$171.8837	$171.88	$171.90	$171.90
Purchase #2	$89.40	12.723%	$100.7744	$100.77	$100.75	$100.80
Purchase #3	$12.91	5.432%	$13.6113	$13.61	$13.60	$13.60
Purchase #4	$149.47	4.232%	$155.7956	$155.80	$155.80	$155.80
Purchase #5	$166.54	7.523%	$179.0688	$179.07	$179.05	$179.10
Purchase #6	$199.50	12.198%	$223.835	$223.84	$223.85	$223.80
Purchase #7	$199.77	9.274%	$218.2967	$218.30	$218.30	$218.30
7 purchase totals =	$970.21		$1,063.2655	$1,063.27	$1,063.25	$1,063.30