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	$93.51	11.756%	$104.503	$104.50	$104.50	$104.50
Purchase #2	$102.83	8.425%	$111.4934	$111.49	$111.50	$111.50
Purchase #3	$66.45	10.834%	$73.6492	$73.65	$73.65	$73.60
Purchase #4	$194.73	11.412%	$216.9526	$216.95	$216.95	$217.00
Purchase #5	$41.90	13.490%	$47.5523	$47.55	$47.55	$47.60
Purchase #6	$213.37	7.248%	$228.8351	$228.84	$228.85	$228.80
Purchase #7	$145.29	13.244%	$164.5322	$164.53	$164.55	$164.50
7 purchase totals =	$858.08		$947.5178	$947.51	$947.55	$947.50