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	$95.88	13.303%	$108.6349	$108.63	$108.65	$108.60
Purchase #2	$204.66	6.427%	$217.8135	$217.81	$217.80	$217.80
Purchase #3	$33.65	11.462%	$37.507	$37.51	$37.50	$37.50
Purchase #4	$86.65	5.399%	$91.3282	$91.33	$91.35	$91.30
Purchase #5	$130.43	8.574%	$141.6131	$141.61	$141.60	$141.60
Purchase #6	$228.33	4.647%	$238.9405	$238.94	$238.95	$238.90
Purchase #7	$187.90	8.340%	$203.5709	$203.57	$203.55	$203.60
7 purchase totals =	$967.50		$1,039.4081	$1,039.40	$1,039.40	$1,039.30