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	$164.62	6.619%	$175.5162	$175.52	$175.50	$175.50
Purchase #2	$155.78	7.533%	$167.5149	$167.51	$167.50	$167.50
Purchase #3	$160.96	12.613%	$181.2619	$181.26	$181.25	$181.30
Purchase #4	$92.78	4.733%	$97.1713	$97.17	$97.15	$97.20
Purchase #5	$148.74	6.419%	$158.2876	$158.29	$158.30	$158.30
Purchase #6	$98.88	11.181%	$109.9358	$109.94	$109.95	$109.90
Purchase #7	$67.70	6.853%	$72.3395	$72.34	$72.35	$72.30
7 purchase totals =	$889.46		$962.0272	$962.03	$962.00	$962.00