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	$130.95	10.435%	$144.6146	$144.61	$144.60	$144.60
Purchase #2	$159.46	12.801%	$179.8725	$179.87	$179.85	$179.90
Purchase #3	$55.83	5.210%	$58.7387	$58.74	$58.75	$58.70
Purchase #4	$129.66	9.116%	$141.4798	$141.48	$141.50	$141.50
Purchase #5	$85.88	4.632%	$89.858	$89.86	$89.85	$89.90
Purchase #6	$140.28	3.169%	$144.7255	$144.73	$144.75	$144.70
Purchase #7	$113.48	7.600%	$122.1045	$122.10	$122.10	$122.10
7 purchase totals =	$815.54		$881.3936	$881.39	$881.40	$881.40