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	$121.71	7.239%	$130.5206	$130.52	$130.50	$130.50
Purchase #2	$133.47	13.636%	$151.67	$151.67	$151.65	$151.70
Purchase #3	$155.78	5.830%	$164.862	$164.86	$164.85	$164.90
Purchase #4	$116.76	7.382%	$125.3792	$125.38	$125.40	$125.40
Purchase #5	$101.89	6.477%	$108.4894	$108.49	$108.50	$108.50
Purchase #6	$221.41	4.619%	$231.6369	$231.64	$231.65	$231.60
Purchase #7	$235.96	9.755%	$258.9779	$258.98	$259.00	$259.00
7 purchase totals =	$1,086.98		$1,171.5360	$1,171.54	$1,171.55	$1,171.60