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	$35.89	3.612%	$37.1863	$37.19	$37.20	$37.20
Purchase #2	$48.29	8.730%	$52.5057	$52.51	$52.50	$52.50
Purchase #3	$69.74	10.663%	$77.1764	$77.18	$77.20	$77.20
Purchase #4	$168.64	10.235%	$185.9003	$185.90	$185.90	$185.90
Purchase #5	$64.50	5.273%	$67.9011	$67.90	$67.90	$67.90
Purchase #6	$14.69	4.330%	$15.3261	$15.33	$15.35	$15.30
Purchase #7	$204.64	11.254%	$227.6702	$227.67	$227.65	$227.70
7 purchase totals =	$606.39		$663.6661	$663.68	$663.70	$663.70