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	$167.85	7.665%	$180.7157	$180.72	$180.70	$180.70
Purchase #2	$55.64	11.560%	$62.072	$62.07	$62.05	$62.10
Purchase #3	$180.51	5.552%	$190.5319	$190.53	$190.55	$190.50
Purchase #4	$69.25	7.191%	$74.2298	$74.23	$74.25	$74.20
Purchase #5	$83.86	7.190%	$89.8895	$89.89	$89.90	$89.90
Purchase #6	$23.79	11.660%	$26.5639	$26.56	$26.55	$26.60
Purchase #7	$206.85	8.720%	$224.8873	$224.89	$224.90	$224.90
7 purchase totals =	$787.75		$848.8901	$848.89	$848.90	$848.90