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	$115.86	9.813%	$127.2293	$127.23	$127.25	$127.20
Purchase #2	$138.50	13.142%	$156.7017	$156.70	$156.70	$156.70
Purchase #3	$77.29	11.205%	$85.9503	$85.95	$85.95	$86.00
Purchase #4	$59.34	3.506%	$61.4205	$61.42	$61.40	$61.40
Purchase #5	$66.59	13.340%	$75.4731	$75.47	$75.45	$75.50
Purchase #6	$32.80	11.641%	$36.6182	$36.62	$36.60	$36.60
Purchase #7	$193.53	9.460%	$211.8379	$211.84	$211.85	$211.80
7 purchase totals =	$683.91		$755.2310	$755.23	$755.20	$755.20