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	$161.88	5.462%	$170.7219	$170.72	$170.70	$170.70
Purchase #2	$47.63	3.176%	$49.1427	$49.14	$49.15	$49.10
Purchase #3	$112.88	3.546%	$116.8827	$116.88	$116.90	$116.90
Purchase #4	$75.80	10.418%	$83.6968	$83.70	$83.70	$83.70
Purchase #5	$150.82	3.142%	$155.5588	$155.56	$155.55	$155.60
Purchase #6	$54.57	13.345%	$61.8524	$61.85	$61.85	$61.90
Purchase #7	$56.34	10.601%	$62.3126	$62.31	$62.30	$62.30
7 purchase totals =	$659.92		$700.1679	$700.16	$700.15	$700.20