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	$31.43	5.528%	$33.1675	$33.17	$33.15	$33.20
Purchase #2	$246.72	7.626%	$265.5349	$265.53	$265.55	$265.50
Purchase #3	$155.50	6.289%	$165.2794	$165.28	$165.30	$165.30
Purchase #4	$30.83	13.102%	$34.8693	$34.87	$34.85	$34.90
Purchase #5	$55.85	6.507%	$59.4842	$59.48	$59.50	$59.50
Purchase #6	$249.74	3.526%	$258.5458	$258.55	$258.55	$258.50
Purchase #7	$204.47	7.810%	$220.4391	$220.44	$220.45	$220.40
7 purchase totals =	$974.54		$1,037.3202	$1,037.32	$1,037.35	$1,037.30