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	$86.45	8.335%	$93.6556	$93.66	$93.65	$93.70
Purchase #2	$156.65	10.361%	$172.8805	$172.88	$172.90	$172.90
Purchase #3	$136.76	12.556%	$153.9316	$153.93	$153.95	$153.90
Purchase #4	$99.42	10.243%	$109.6036	$109.60	$109.60	$109.60
Purchase #5	$74.86	3.243%	$77.2877	$77.29	$77.30	$77.30
Purchase #6	$201.81	9.238%	$220.4532	$220.45	$220.45	$220.50
Purchase #7	$159.54	8.264%	$172.7244	$172.72	$172.70	$172.70
7 purchase totals =	$915.49		$1,000.5366	$1,000.53	$1,000.55	$1,000.60