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	$43.82	4.154%	$45.6403	$45.64	$45.65	$45.60
Purchase #2	$64.32	9.620%	$70.5076	$70.51	$70.50	$70.50
Purchase #3	$26.65	6.140%	$28.2863	$28.29	$28.30	$28.30
Purchase #4	$53.32	8.523%	$57.8645	$57.86	$57.85	$57.90
Purchase #5	$97.62	6.774%	$104.2328	$104.23	$104.25	$104.20
Purchase #6	$212.69	13.806%	$242.054	$242.05	$242.05	$242.10
Purchase #7	$52.85	10.625%	$58.4653	$58.47	$58.45	$58.50
7 purchase totals =	$551.27		$607.0508	$607.05	$607.05	$607.10