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	$93.64	6.340%	$99.5768	$99.58	$99.60	$99.60
Purchase #2	$43.39	7.410%	$46.6052	$46.61	$46.60	$46.60
Purchase #3	$23.72	6.632%	$25.2931	$25.29	$25.30	$25.30
Purchase #4	$136.61	6.516%	$145.5115	$145.51	$145.50	$145.50
Purchase #5	$164.80	7.298%	$176.8271	$176.83	$176.85	$176.80
Purchase #6	$128.88	13.679%	$146.5095	$146.51	$146.50	$146.50
Purchase #7	$83.74	12.545%	$94.2452	$94.25	$94.25	$94.20
7 purchase totals =	$674.78		$734.5684	$734.58	$734.60	$734.50