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	$103.86	7.231%	$111.3701	$111.37	$111.35	$111.40
Purchase #2	$36.49	4.115%	$37.9916	$37.99	$38.00	$38.00
Purchase #3	$53.52	10.595%	$59.1904	$59.19	$59.20	$59.20
Purchase #4	$178.48	12.539%	$200.8596	$200.86	$200.85	$200.90
Purchase #5	$10.50	9.359%	$11.4827	$11.48	$11.50	$11.50
Purchase #6	$245.57	12.826%	$277.0668	$277.07	$277.05	$277.10
Purchase #7	$133.46	11.574%	$148.9067	$148.91	$148.90	$148.90
7 purchase totals =	$761.88		$846.8679	$846.87	$846.85	$847.00