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	$93.78	11.655%	$104.7101	$104.71	$104.70	$104.70
Purchase #2	$190.50	3.167%	$196.5331	$196.53	$196.55	$196.50
Purchase #3	$247.61	3.693%	$256.7542	$256.75	$256.75	$256.80
Purchase #4	$131.99	13.659%	$150.0185	$150.02	$150.00	$150.00
Purchase #5	$158.63	10.219%	$174.8404	$174.84	$174.85	$174.80
Purchase #6	$178.79	9.785%	$196.2846	$196.28	$196.30	$196.30
Purchase #7	$69.51	10.115%	$76.5409	$76.54	$76.55	$76.50
7 purchase totals =	$1,070.81		$1,155.6818	$1,155.67	$1,155.70	$1,155.60