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	$188.65	3.218%	$194.7208	$194.72	$194.70	$194.70
Purchase #2	$228.95	6.478%	$243.7814	$243.78	$243.80	$243.80
Purchase #3	$65.53	11.192%	$72.8641	$72.86	$72.85	$72.90
Purchase #4	$143.89	8.111%	$155.5609	$155.56	$155.55	$155.60
Purchase #5	$77.50	4.604%	$81.0681	$81.07	$81.05	$81.10
Purchase #6	$10.43	10.119%	$11.4854	$11.49	$11.50	$11.50
Purchase #7	$90.69	7.121%	$97.148	$97.15	$97.15	$97.10
7 purchase totals =	$805.64		$856.6287	$856.63	$856.60	$856.70