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	$76.30	7.662%	$82.1461	$82.15	$82.15	$82.10
Purchase #2	$167.65	6.225%	$178.0862	$178.09	$178.10	$178.10
Purchase #3	$126.39	7.422%	$135.7707	$135.77	$135.75	$135.80
Purchase #4	$196.39	7.384%	$210.8914	$210.89	$210.90	$210.90
Purchase #5	$208.57	5.726%	$220.5127	$220.51	$220.50	$220.50
Purchase #6	$152.82	3.404%	$158.022	$158.02	$158.00	$158.00
Purchase #7	$146.44	4.157%	$152.5275	$152.53	$152.55	$152.50
7 purchase totals =	$1,074.56		$1,137.9566	$1,137.96	$1,137.95	$1,137.90