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	$78.36	10.610%	$86.674	$86.67	$86.65	$86.70
Purchase #2	$190.76	13.609%	$216.7205	$216.72	$216.70	$216.70
Purchase #3	$149.63	7.254%	$160.4842	$160.48	$160.50	$160.50
Purchase #4	$217.94	5.767%	$230.5086	$230.51	$230.50	$230.50
Purchase #5	$145.71	7.625%	$156.8204	$156.82	$156.80	$156.80
Purchase #6	$113.80	9.419%	$124.5188	$124.52	$124.50	$124.50
Purchase #7	$24.81	4.105%	$25.8285	$25.83	$25.85	$25.80
7 purchase totals =	$921.01		$1,001.5550	$1,001.55	$1,001.50	$1,001.50