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	$105.41	6.166%	$111.9096	$111.91	$111.90	$111.90
Purchase #2	$36.93	12.871%	$41.6833	$41.68	$41.70	$41.70
Purchase #3	$117.72	3.476%	$121.8119	$121.81	$121.80	$121.80
Purchase #4	$150.89	13.231%	$170.8543	$170.85	$170.85	$170.90
Purchase #5	$81.25	11.535%	$90.6222	$90.62	$90.60	$90.60
Purchase #6	$115.58	13.832%	$131.567	$131.57	$131.55	$131.60
Purchase #7	$55.35	3.500%	$57.2873	$57.29	$57.30	$57.30
7 purchase totals =	$663.13		$725.7356	$725.73	$725.70	$725.80