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	$49.62	12.226%	$55.6865	$55.69	$55.70	$55.70
Purchase #2	$60.42	8.807%	$65.7412	$65.74	$65.75	$65.70
Purchase #3	$160.41	13.363%	$181.8456	$181.85	$181.85	$181.80
Purchase #4	$244.70	12.598%	$275.5273	$275.53	$275.55	$275.50
Purchase #5	$217.48	5.497%	$229.4349	$229.43	$229.45	$229.40
Purchase #6	$92.51	7.407%	$99.3622	$99.36	$99.35	$99.40
Purchase #7	$93.71	7.298%	$100.549	$100.55	$100.55	$100.50
7 purchase totals =	$918.85		$1,008.1467	$1,008.15	$1,008.20	$1,008.00