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	$104.57	11.538%	$116.6353	$116.64	$116.65	$116.60
Purchase #2	$51.51	8.619%	$55.9496	$55.95	$55.95	$55.90
Purchase #3	$223.32	3.800%	$231.8062	$231.81	$231.80	$231.80
Purchase #4	$174.47	12.486%	$196.2543	$196.25	$196.25	$196.30
Purchase #5	$93.57	12.521%	$105.2859	$105.29	$105.30	$105.30
Purchase #6	$141.33	5.104%	$148.5435	$148.54	$148.55	$148.50
Purchase #7	$107.59	13.441%	$122.0512	$122.05	$122.05	$122.10
7 purchase totals =	$896.36		$976.5260	$976.53	$976.55	$976.50