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	$130.84	13.778%	$148.8671	$148.87	$148.85	$148.90
Purchase #2	$38.59	3.300%	$39.8635	$39.86	$39.85	$39.90
Purchase #3	$30.44	7.456%	$32.7096	$32.71	$32.70	$32.70
Purchase #4	$89.47	5.538%	$94.4248	$94.42	$94.40	$94.40
Purchase #5	$109.93	11.263%	$122.3114	$122.31	$122.30	$122.30
Purchase #6	$125.65	9.255%	$137.2789	$137.28	$137.30	$137.30
Purchase #7	$72.73	7.818%	$78.416	$78.42	$78.40	$78.40
7 purchase totals =	$597.65		$653.8713	$653.87	$653.80	$653.90