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	$188.28	12.500%	$211.815	$211.82	$211.80	$211.80
Purchase #2	$115.97	13.369%	$131.474	$131.47	$131.45	$131.50
Purchase #3	$198.60	8.513%	$215.5068	$215.51	$215.50	$215.50
Purchase #4	$144.55	5.521%	$152.5306	$152.53	$152.55	$152.50
Purchase #5	$41.46	10.714%	$45.902	$45.90	$45.90	$45.90
Purchase #6	$30.66	5.648%	$32.3917	$32.39	$32.40	$32.40
Purchase #7	$138.85	3.314%	$143.4515	$143.45	$143.45	$143.50
7 purchase totals =	$858.37		$933.0716	$933.07	$933.05	$933.10