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	$172.31	10.533%	$190.4594	$190.46	$190.45	$190.50
Purchase #2	$43.29	12.804%	$48.8329	$48.83	$48.85	$48.80
Purchase #3	$124.42	6.834%	$132.9229	$132.92	$132.90	$132.90
Purchase #4	$38.88	8.660%	$42.247	$42.25	$42.25	$42.20
Purchase #5	$67.34	4.130%	$70.1211	$70.12	$70.10	$70.10
Purchase #6	$105.51	6.587%	$112.4599	$112.46	$112.45	$112.50
Purchase #7	$97.73	13.345%	$110.7721	$110.77	$110.75	$110.80
7 purchase totals =	$649.48		$707.8153	$707.81	$707.75	$707.80