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	$42.71	4.694%	$44.7148	$44.71	$44.70	$44.70
Purchase #2	$73.75	11.365%	$82.1317	$82.13	$82.15	$82.10
Purchase #3	$65.44	8.576%	$71.0521	$71.05	$71.05	$71.10
Purchase #4	$63.48	13.327%	$71.94	$71.94	$71.95	$71.90
Purchase #5	$121.52	8.449%	$131.7872	$131.79	$131.80	$131.80
Purchase #6	$10.67	7.717%	$11.4934	$11.49	$11.50	$11.50
Purchase #7	$205.53	13.780%	$233.852	$233.85	$233.85	$233.90
7 purchase totals =	$583.10		$646.9712	$646.96	$647.00	$647.00