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	$232.27	11.748%	$259.5571	$259.56	$259.55	$259.60
Purchase #2	$56.74	8.672%	$61.6605	$61.66	$61.65	$61.70
Purchase #3	$153.32	12.735%	$172.8453	$172.85	$172.85	$172.80
Purchase #4	$203.62	4.514%	$212.8114	$212.81	$212.80	$212.80
Purchase #5	$25.53	5.435%	$26.9176	$26.92	$26.90	$26.90
Purchase #6	$245.66	3.495%	$254.2458	$254.25	$254.25	$254.20
Purchase #7	$100.57	8.274%	$108.8912	$108.89	$108.90	$108.90
7 purchase totals =	$1,017.71		$1,096.9289	$1,096.94	$1,096.90	$1,096.90