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	$217.52	7.416%	$233.6513	$233.65	$233.65	$233.70
Purchase #2	$239.80	11.560%	$267.5209	$267.52	$267.50	$267.50
Purchase #3	$184.27	8.502%	$199.9366	$199.94	$199.95	$199.90
Purchase #4	$193.66	7.676%	$208.5253	$208.53	$208.55	$208.50
Purchase #5	$104.54	4.866%	$109.6269	$109.63	$109.65	$109.60
Purchase #6	$31.29	6.824%	$33.4252	$33.43	$33.45	$33.40
Purchase #7	$39.88	13.707%	$45.3464	$45.35	$45.35	$45.30
7 purchase totals =	$1,010.96		$1,098.0326	$1,098.05	$1,098.10	$1,097.90