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	$155.34	4.612%	$162.5043	$162.50	$162.50	$162.50
Purchase #2	$95.77	5.283%	$100.8295	$100.83	$100.85	$100.80
Purchase #3	$177.52	12.769%	$200.1875	$200.19	$200.20	$200.20
Purchase #4	$72.44	9.522%	$79.3377	$79.34	$79.35	$79.30
Purchase #5	$244.94	7.137%	$262.4214	$262.42	$262.40	$262.40
Purchase #6	$100.50	8.865%	$109.4093	$109.41	$109.40	$109.40
Purchase #7	$217.93	13.601%	$247.5707	$247.57	$247.55	$247.60
7 purchase totals =	$1,064.44		$1,162.2604	$1,162.26	$1,162.25	$1,162.20