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	$48.51	9.814%	$53.2708	$53.27	$53.25	$53.30
Purchase #2	$172.89	9.204%	$188.8028	$188.80	$188.80	$188.80
Purchase #3	$89.44	5.708%	$94.5452	$94.55	$94.55	$94.50
Purchase #4	$138.73	10.199%	$152.8791	$152.88	$152.90	$152.90
Purchase #5	$129.51	5.554%	$136.703	$136.70	$136.70	$136.70
Purchase #6	$248.35	3.428%	$256.8634	$256.86	$256.85	$256.90
Purchase #7	$56.54	10.493%	$62.4727	$62.47	$62.45	$62.50
7 purchase totals =	$883.97		$945.5370	$945.53	$945.50	$945.60