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	$105.89	8.528%	$114.9203	$114.92	$114.90	$114.90
Purchase #2	$10.39	9.243%	$11.3503	$11.35	$11.35	$11.40
Purchase #3	$149.44	10.855%	$165.6617	$165.66	$165.65	$165.70
Purchase #4	$150.86	9.587%	$165.3229	$165.32	$165.30	$165.30
Purchase #5	$88.89	10.414%	$98.147	$98.15	$98.15	$98.10
Purchase #6	$217.85	6.141%	$231.2282	$231.23	$231.25	$231.20
Purchase #7	$77.27	8.324%	$83.702	$83.70	$83.70	$83.70
7 purchase totals =	$800.59		$870.3324	$870.33	$870.30	$870.30