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	$64.37	12.677%	$72.5302	$72.53	$72.55	$72.50
Purchase #2	$124.33	8.513%	$134.9142	$134.91	$134.90	$134.90
Purchase #3	$17.73	6.130%	$18.8168	$18.82	$18.80	$18.80
Purchase #4	$46.55	12.355%	$52.3013	$52.30	$52.30	$52.30
Purchase #5	$186.87	6.569%	$199.1455	$199.15	$199.15	$199.10
Purchase #6	$212.52	4.376%	$221.8199	$221.82	$221.80	$221.80
Purchase #7	$231.46	10.670%	$256.1568	$256.16	$256.15	$256.20
7 purchase totals =	$883.83		$955.6847	$955.69	$955.65	$955.60