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	$40.60	10.655%	$44.9259	$44.93	$44.95	$44.90
Purchase #2	$37.66	3.276%	$38.8937	$38.89	$38.90	$38.90
Purchase #3	$150.43	11.324%	$167.4647	$167.46	$167.45	$167.50
Purchase #4	$85.34	4.438%	$89.1274	$89.13	$89.15	$89.10
Purchase #5	$246.77	11.666%	$275.5582	$275.56	$275.55	$275.60
Purchase #6	$204.82	10.367%	$226.0537	$226.05	$226.05	$226.10
Purchase #7	$119.57	5.330%	$125.9431	$125.94	$125.95	$125.90
7 purchase totals =	$885.19		$967.9667	$967.96	$968.00	$968.00