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	$126.53	11.468%	$141.0405	$141.04	$141.05	$141.00
Purchase #2	$41.85	13.146%	$47.3516	$47.35	$47.35	$47.40
Purchase #3	$142.37	5.634%	$150.3911	$150.39	$150.40	$150.40
Purchase #4	$82.99	10.750%	$91.9114	$91.91	$91.90	$91.90
Purchase #5	$144.63	4.689%	$151.4117	$151.41	$151.40	$151.40
Purchase #6	$66.91	9.831%	$73.4879	$73.49	$73.50	$73.50
Purchase #7	$95.58	4.521%	$99.9012	$99.90	$99.90	$99.90
7 purchase totals =	$700.86		$755.4954	$755.49	$755.50	$755.50