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	$206.67	7.588%	$222.3521	$222.35	$222.35	$222.40
Purchase #2	$105.28	6.328%	$111.9421	$111.94	$111.95	$111.90
Purchase #3	$187.38	6.469%	$199.5016	$199.50	$199.50	$199.50
Purchase #4	$145.41	9.333%	$158.9811	$158.98	$159.00	$159.00
Purchase #5	$215.38	6.830%	$230.0905	$230.09	$230.10	$230.10
Purchase #6	$192.49	12.155%	$215.8872	$215.89	$215.90	$215.90
Purchase #7	$172.53	10.282%	$190.2695	$190.27	$190.25	$190.30
7 purchase totals =	$1,225.14		$1,329.0241	$1,329.02	$1,329.05	$1,329.10