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	$47.47	7.219%	$50.8969	$50.90	$50.90	$50.90
Purchase #2	$43.60	7.359%	$46.8085	$46.81	$46.80	$46.80
Purchase #3	$97.40	6.647%	$103.8742	$103.87	$103.85	$103.90
Purchase #4	$174.88	7.257%	$187.571	$187.57	$187.55	$187.60
Purchase #5	$121.32	12.667%	$136.6876	$136.69	$136.70	$136.70
Purchase #6	$150.37	12.111%	$168.5813	$168.58	$168.60	$168.60
Purchase #7	$30.25	8.801%	$32.9123	$32.91	$32.90	$32.90
7 purchase totals =	$665.29		$727.3318	$727.33	$727.30	$727.40