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	$184.81	3.636%	$191.5297	$191.53	$191.55	$191.50
Purchase #2	$164.61	12.440%	$185.0875	$185.09	$185.10	$185.10
Purchase #3	$119.29	12.447%	$134.138	$134.14	$134.15	$134.10
Purchase #4	$71.40	6.680%	$76.1695	$76.17	$76.15	$76.20
Purchase #5	$200.93	8.779%	$218.5696	$218.57	$218.55	$218.60
Purchase #6	$199.70	5.619%	$210.9211	$210.92	$210.90	$210.90
Purchase #7	$40.26	12.511%	$45.2969	$45.30	$45.30	$45.30
7 purchase totals =	$981.00		$1,061.7123	$1,061.72	$1,061.70	$1,061.70