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	$173.83	12.130%	$194.9156	$194.92	$194.90	$194.90
Purchase #2	$220.82	4.755%	$231.32	$231.32	$231.30	$231.30
Purchase #3	$56.51	11.708%	$63.1262	$63.13	$63.15	$63.10
Purchase #4	$83.85	11.505%	$93.4969	$93.50	$93.50	$93.50
Purchase #5	$120.33	6.760%	$128.4643	$128.46	$128.45	$128.50
Purchase #6	$10.72	5.279%	$11.2859	$11.29	$11.30	$11.30
Purchase #7	$10.93	8.421%	$11.8504	$11.85	$11.85	$11.90
7 purchase totals =	$676.99		$734.4593	$734.47	$734.45	$734.50