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	$222.46	6.650%	$237.2536	$237.25	$237.25	$237.30
Purchase #2	$11.76	13.221%	$13.3148	$13.31	$13.30	$13.30
Purchase #3	$61.52	4.266%	$64.1444	$64.14	$64.15	$64.10
Purchase #4	$48.92	6.405%	$52.0533	$52.05	$52.05	$52.10
Purchase #5	$80.79	11.515%	$90.093	$90.09	$90.10	$90.10
Purchase #6	$20.82	10.141%	$22.9314	$22.93	$22.95	$22.90
Purchase #7	$144.50	7.300%	$155.0485	$155.05	$155.05	$155.00
7 purchase totals =	$590.77		$634.8390	$634.82	$634.85	$634.80