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	$177.65	7.292%	$190.6042	$190.60	$190.60	$190.60
Purchase #2	$19.51	13.529%	$22.1495	$22.15	$22.15	$22.10
Purchase #3	$40.60	11.102%	$45.1074	$45.11	$45.10	$45.10
Purchase #4	$242.67	7.142%	$260.0015	$260.00	$260.00	$260.00
Purchase #5	$116.54	5.872%	$123.3832	$123.38	$123.40	$123.40
Purchase #6	$37.86	7.258%	$40.6079	$40.61	$40.60	$40.60
Purchase #7	$182.71	6.198%	$194.0344	$194.03	$194.05	$194.00
7 purchase totals =	$817.54		$875.8881	$875.88	$875.90	$875.80