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	$49.53	13.516%	$56.2245	$56.22	$56.20	$56.20
Purchase #2	$193.93	13.725%	$220.5469	$220.55	$220.55	$220.50
Purchase #3	$171.86	13.227%	$194.5919	$194.59	$194.60	$194.60
Purchase #4	$71.73	7.871%	$77.3759	$77.38	$77.40	$77.40
Purchase #5	$43.44	11.297%	$48.3474	$48.35	$48.35	$48.30
Purchase #6	$69.73	4.178%	$72.6433	$72.64	$72.65	$72.60
Purchase #7	$59.65	10.289%	$65.7874	$65.79	$65.80	$65.80
7 purchase totals =	$659.87		$735.5173	$735.52	$735.55	$735.40