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	$35.91	3.827%	$37.2843	$37.28	$37.30	$37.30
Purchase #2	$99.72	9.597%	$109.2901	$109.29	$109.30	$109.30
Purchase #3	$102.45	5.593%	$108.18	$108.18	$108.20	$108.20
Purchase #4	$149.98	10.709%	$166.0414	$166.04	$166.05	$166.00
Purchase #5	$82.86	8.238%	$89.686	$89.69	$89.70	$89.70
Purchase #6	$212.44	5.340%	$223.7843	$223.78	$223.80	$223.80
Purchase #7	$221.51	13.412%	$251.2189	$251.22	$251.20	$251.20
7 purchase totals =	$904.87		$985.4850	$985.48	$985.55	$985.50