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	$147.83	7.503%	$158.9217	$158.92	$158.90	$158.90
Purchase #2	$143.49	10.304%	$158.2752	$158.28	$158.30	$158.30
Purchase #3	$127.48	12.833%	$143.8395	$143.84	$143.85	$143.80
Purchase #4	$40.60	5.313%	$42.7571	$42.76	$42.75	$42.80
Purchase #5	$108.37	7.136%	$116.1033	$116.10	$116.10	$116.10
Purchase #6	$73.44	5.531%	$77.502	$77.50	$77.50	$77.50
Purchase #7	$105.58	4.642%	$110.481	$110.48	$110.50	$110.50
7 purchase totals =	$746.79		$807.8798	$807.88	$807.90	$807.90