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	$65.64	5.468%	$69.2292	$69.23	$69.25	$69.20
Purchase #2	$74.29	6.176%	$78.8782	$78.88	$78.90	$78.90
Purchase #3	$68.43	12.712%	$77.1288	$77.13	$77.15	$77.10
Purchase #4	$51.39	5.369%	$54.1491	$54.15	$54.15	$54.10
Purchase #5	$65.78	7.432%	$70.6688	$70.67	$70.65	$70.70
Purchase #6	$11.84	6.171%	$12.5706	$12.57	$12.55	$12.60
Purchase #7	$130.97	9.602%	$143.5457	$143.55	$143.55	$143.50
7 purchase totals =	$468.34		$506.1704	$506.18	$506.20	$506.10