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	$88.75	6.106%	$94.1691	$94.17	$94.15	$94.20
Purchase #2	$34.70	7.414%	$37.2727	$37.27	$37.25	$37.30
Purchase #3	$216.27	4.364%	$225.708	$225.71	$225.70	$225.70
Purchase #4	$9.82	6.590%	$10.4671	$10.47	$10.45	$10.50
Purchase #5	$71.56	9.856%	$78.613	$78.61	$78.60	$78.60
Purchase #6	$46.43	11.871%	$51.9417	$51.94	$51.95	$51.90
Purchase #7	$193.98	10.639%	$214.6175	$214.62	$214.60	$214.60
7 purchase totals =	$661.51		$712.7891	$712.79	$712.70	$712.80