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	$33.39	12.308%	$37.4996	$37.50	$37.50	$37.50
Purchase #2	$65.28	12.709%	$73.5764	$73.58	$73.60	$73.60
Purchase #3	$77.96	12.417%	$87.6403	$87.64	$87.65	$87.60
Purchase #4	$232.37	9.126%	$253.5761	$253.58	$253.60	$253.60
Purchase #5	$36.82	6.244%	$39.119	$39.12	$39.10	$39.10
Purchase #6	$52.95	3.650%	$54.8827	$54.88	$54.90	$54.90
Purchase #7	$44.34	3.740%	$45.9983	$46.00	$46.00	$46.00
7 purchase totals =	$543.11		$592.2924	$592.30	$592.35	$592.30