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	$63.77	6.145%	$67.6887	$67.69	$67.70	$67.70
Purchase #2	$176.42	6.646%	$188.1449	$188.14	$188.15	$188.10
Purchase #3	$11.25	3.299%	$11.6211	$11.62	$11.60	$11.60
Purchase #4	$81.25	6.464%	$86.502	$86.50	$86.50	$86.50
Purchase #5	$140.46	3.650%	$145.5868	$145.59	$145.60	$145.60
Purchase #6	$243.63	4.733%	$255.161	$255.16	$255.15	$255.20
Purchase #7	$184.58	3.661%	$191.3375	$191.34	$191.35	$191.30
7 purchase totals =	$901.36		$946.0420	$946.04	$946.05	$946.00