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	$84.41	7.635%	$90.8547	$90.85	$90.85	$90.90
Purchase #2	$218.88	13.823%	$249.1358	$249.14	$249.15	$249.10
Purchase #3	$163.56	13.655%	$185.8941	$185.89	$185.90	$185.90
Purchase #4	$126.88	11.303%	$141.2212	$141.22	$141.20	$141.20
Purchase #5	$95.29	13.605%	$108.2542	$108.25	$108.25	$108.30
Purchase #6	$198.35	10.207%	$218.5956	$218.60	$218.60	$218.60
Purchase #7	$149.89	3.346%	$154.9053	$154.91	$154.90	$154.90
7 purchase totals =	$1,037.26		$1,148.8609	$1,148.86	$1,148.85	$1,148.90