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	$43.75	6.178%	$46.4529	$46.45	$46.45	$46.50
Purchase #2	$121.26	13.712%	$137.8872	$137.89	$137.90	$137.90
Purchase #3	$78.62	6.653%	$83.8506	$83.85	$83.85	$83.90
Purchase #4	$57.48	6.467%	$61.1972	$61.20	$61.20	$61.20
Purchase #5	$62.58	8.326%	$67.7904	$67.79	$67.80	$67.80
Purchase #6	$152.46	6.185%	$161.8897	$161.89	$161.90	$161.90
Purchase #7	$52.65	6.677%	$56.1654	$56.17	$56.15	$56.20
7 purchase totals =	$568.80		$615.2334	$615.24	$615.25	$615.40