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	$153.66	13.180%	$173.9124	$173.91	$173.90	$173.90
Purchase #2	$161.42	6.188%	$171.4087	$171.41	$171.40	$171.40
Purchase #3	$127.29	10.350%	$140.4645	$140.46	$140.45	$140.50
Purchase #4	$92.32	8.513%	$100.1792	$100.18	$100.20	$100.20
Purchase #5	$182.67	10.521%	$201.8887	$201.89	$201.90	$201.90
Purchase #6	$6.84	9.636%	$7.4991	$7.50	$7.50	$7.50
Purchase #7	$183.74	3.477%	$190.1286	$190.13	$190.15	$190.10
7 purchase totals =	$907.94		$985.4812	$985.48	$985.50	$985.50