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	$136.61	10.874%	$151.465	$151.47	$151.45	$151.50
Purchase #2	$28.77	8.634%	$31.254	$31.25	$31.25	$31.30
Purchase #3	$116.69	6.667%	$124.4697	$124.47	$124.45	$124.50
Purchase #4	$50.63	3.511%	$52.4076	$52.41	$52.40	$52.40
Purchase #5	$100.65	9.627%	$110.3396	$110.34	$110.35	$110.30
Purchase #6	$152.72	8.454%	$165.6309	$165.63	$165.65	$165.60
Purchase #7	$111.38	7.802%	$120.0699	$120.07	$120.05	$120.10
7 purchase totals =	$697.45		$755.6367	$755.64	$755.60	$755.70