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	$228.85	8.228%	$247.6798	$247.68	$247.70	$247.70
Purchase #2	$134.72	11.631%	$150.3893	$150.39	$150.40	$150.40
Purchase #3	$82.50	7.369%	$88.5794	$88.58	$88.60	$88.60
Purchase #4	$69.71	8.375%	$75.5482	$75.55	$75.55	$75.50
Purchase #5	$111.59	6.605%	$118.9605	$118.96	$118.95	$119.00
Purchase #6	$117.65	11.788%	$131.5186	$131.52	$131.50	$131.50
Purchase #7	$220.61	10.556%	$243.8976	$243.90	$243.90	$243.90
7 purchase totals =	$965.63		$1,056.5734	$1,056.58	$1,056.60	$1,056.60