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	$140.63	4.422%	$146.8487	$146.85	$146.85	$146.80
Purchase #2	$180.61	5.703%	$190.9102	$190.91	$190.90	$190.90
Purchase #3	$220.27	4.847%	$230.9465	$230.95	$230.95	$230.90
Purchase #4	$56.32	11.591%	$62.8481	$62.85	$62.85	$62.80
Purchase #5	$200.66	3.773%	$208.2309	$208.23	$208.25	$208.20
Purchase #6	$125.58	12.766%	$141.6115	$141.61	$141.60	$141.60
Purchase #7	$56.93	8.829%	$61.9563	$61.96	$61.95	$62.00
7 purchase totals =	$981.00		$1,043.3522	$1,043.36	$1,043.35	$1,043.20