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	$106.89	5.246%	$112.4974	$112.50	$112.50	$112.50
Purchase #2	$42.32	6.621%	$45.122	$45.12	$45.10	$45.10
Purchase #3	$62.60	3.184%	$64.5932	$64.59	$64.60	$64.60
Purchase #4	$45.92	10.305%	$50.6521	$50.65	$50.65	$50.70
Purchase #5	$150.53	4.651%	$157.5312	$157.53	$157.55	$157.50
Purchase #6	$232.39	10.411%	$256.5841	$256.58	$256.60	$256.60
Purchase #7	$95.55	13.390%	$108.3441	$108.34	$108.35	$108.30
7 purchase totals =	$736.20		$795.3241	$795.31	$795.35	$795.30