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	$150.93	9.472%	$165.2261	$165.23	$165.25	$165.20
Purchase #2	$70.75	7.820%	$76.2827	$76.28	$76.30	$76.30
Purchase #3	$77.96	10.102%	$85.8355	$85.84	$85.85	$85.80
Purchase #4	$81.64	11.400%	$90.947	$90.95	$90.95	$90.90
Purchase #5	$58.49	8.107%	$63.2318	$63.23	$63.25	$63.20
Purchase #6	$247.40	13.198%	$280.0519	$280.05	$280.05	$280.10
Purchase #7	$188.65	13.689%	$214.4743	$214.47	$214.45	$214.50
7 purchase totals =	$875.82		$976.0493	$976.05	$976.10	$976.00