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	$30.62	10.285%	$33.7693	$33.77	$33.75	$33.80
Purchase #2	$136.80	11.778%	$152.9123	$152.91	$152.90	$152.90
Purchase #3	$222.55	5.111%	$233.9245	$233.92	$233.90	$233.90
Purchase #4	$63.46	11.516%	$70.7681	$70.77	$70.75	$70.80
Purchase #5	$85.90	9.354%	$93.9351	$93.94	$93.95	$93.90
Purchase #6	$240.36	12.776%	$271.0684	$271.07	$271.05	$271.10
Purchase #7	$68.78	12.730%	$77.5357	$77.54	$77.55	$77.50
7 purchase totals =	$848.47		$933.9134	$933.92	$933.85	$933.90