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	$93.49	8.569%	$101.5012	$101.50	$101.50	$101.50
Purchase #2	$159.25	3.667%	$165.0897	$165.09	$165.10	$165.10
Purchase #3	$70.78	12.711%	$79.7768	$79.78	$79.80	$79.80
Purchase #4	$165.97	6.477%	$176.7199	$176.72	$176.70	$176.70
Purchase #5	$6.95	8.158%	$7.517	$7.52	$7.50	$7.50
Purchase #6	$93.46	5.813%	$98.8928	$98.89	$98.90	$98.90
Purchase #7	$88.58	13.375%	$100.4276	$100.43	$100.45	$100.40
7 purchase totals =	$678.48		$729.9250	$729.93	$729.95	$729.90