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	$47.25	12.666%	$53.2347	$53.23	$53.25	$53.20
Purchase #2	$148.78	8.733%	$161.773	$161.77	$161.75	$161.80
Purchase #3	$11.72	11.777%	$13.1003	$13.10	$13.10	$13.10
Purchase #4	$167.71	8.155%	$181.3868	$181.39	$181.40	$181.40
Purchase #5	$231.72	6.371%	$246.4829	$246.48	$246.50	$246.50
Purchase #6	$6.93	6.730%	$7.3964	$7.40	$7.40	$7.40
Purchase #7	$53.94	10.350%	$59.5228	$59.52	$59.50	$59.50
7 purchase totals =	$668.05		$722.8969	$722.89	$722.90	$722.90