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	$82.85	3.467%	$85.7224	$85.72	$85.70	$85.70
Purchase #2	$120.85	5.126%	$127.0448	$127.04	$127.05	$127.00
Purchase #3	$159.65	4.305%	$166.5229	$166.52	$166.50	$166.50
Purchase #4	$68.90	12.433%	$77.4663	$77.47	$77.45	$77.50
Purchase #5	$209.76	5.743%	$221.8065	$221.81	$221.80	$221.80
Purchase #6	$224.41	13.400%	$254.4809	$254.48	$254.50	$254.50
Purchase #7	$113.30	9.751%	$124.3479	$124.35	$124.35	$124.30
7 purchase totals =	$979.72		$1,057.3917	$1,057.39	$1,057.35	$1,057.30