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	$156.46	10.264%	$172.5191	$172.52	$172.50	$172.50
Purchase #2	$57.63	10.841%	$63.8777	$63.88	$63.90	$63.90
Purchase #3	$130.87	10.636%	$144.7893	$144.79	$144.80	$144.80
Purchase #4	$47.76	12.347%	$53.6569	$53.66	$53.65	$53.70
Purchase #5	$205.93	13.503%	$233.7367	$233.74	$233.75	$233.70
Purchase #6	$201.50	13.578%	$228.8597	$228.86	$228.85	$228.90
Purchase #7	$42.37	10.632%	$46.8748	$46.87	$46.85	$46.90
7 purchase totals =	$842.52		$944.3142	$944.32	$944.30	$944.40