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	$7.31	3.707%	$7.581	$7.58	$7.60	$7.60
Purchase #2	$204.57	8.507%	$221.9728	$221.97	$221.95	$222.00
Purchase #3	$199.76	10.507%	$220.7488	$220.75	$220.75	$220.70
Purchase #4	$194.33	5.433%	$204.8879	$204.89	$204.90	$204.90
Purchase #5	$208.73	6.565%	$222.4331	$222.43	$222.45	$222.40
Purchase #6	$219.86	8.469%	$238.4799	$238.48	$238.50	$238.50
Purchase #7	$89.31	10.157%	$98.3812	$98.38	$98.40	$98.40
7 purchase totals =	$1,123.87		$1,214.4847	$1,214.48	$1,214.55	$1,214.50