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	$161.95	4.572%	$169.3544	$169.35	$169.35	$169.40
Purchase #2	$139.70	8.386%	$151.4152	$151.42	$151.40	$151.40
Purchase #3	$59.59	4.464%	$62.2501	$62.25	$62.25	$62.30
Purchase #4	$100.78	9.689%	$110.5446	$110.54	$110.55	$110.50
Purchase #5	$79.87	12.616%	$89.9464	$89.95	$89.95	$89.90
Purchase #6	$165.47	3.433%	$171.1506	$171.15	$171.15	$171.20
Purchase #7	$104.27	11.366%	$116.1213	$116.12	$116.10	$116.10
7 purchase totals =	$811.63		$870.7826	$870.78	$870.75	$870.80