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	$180.91	4.205%	$188.5173	$188.52	$188.50	$188.50
Purchase #2	$60.90	10.843%	$67.5034	$67.50	$67.50	$67.50
Purchase #3	$177.72	10.312%	$196.0465	$196.05	$196.05	$196.00
Purchase #4	$170.79	6.726%	$182.2773	$182.28	$182.30	$182.30
Purchase #5	$118.65	5.201%	$124.821	$124.82	$124.80	$124.80
Purchase #6	$217.49	5.211%	$228.8234	$228.82	$228.80	$228.80
Purchase #7	$75.99	10.393%	$83.8876	$83.89	$83.90	$83.90
7 purchase totals =	$1,002.45		$1,071.8765	$1,071.88	$1,071.85	$1,071.80