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	$150.71	9.836%	$165.5338	$165.53	$165.55	$165.50
Purchase #2	$84.26	9.104%	$91.931	$91.93	$91.95	$91.90
Purchase #3	$217.43	12.323%	$244.2239	$244.22	$244.20	$244.20
Purchase #4	$65.82	8.653%	$71.5154	$71.52	$71.50	$71.50
Purchase #5	$102.64	6.578%	$109.3917	$109.39	$109.40	$109.40
Purchase #6	$38.66	3.125%	$39.8681	$39.87	$39.85	$39.90
Purchase #7	$33.41	8.399%	$36.2161	$36.22	$36.20	$36.20
7 purchase totals =	$692.93		$758.6800	$758.68	$758.65	$758.60