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	$36.32	13.833%	$41.3441	$41.34	$41.35	$41.30
Purchase #2	$20.78	9.772%	$22.8106	$22.81	$22.80	$22.80
Purchase #3	$167.56	3.781%	$173.8954	$173.90	$173.90	$173.90
Purchase #4	$212.73	5.157%	$223.7005	$223.70	$223.70	$223.70
Purchase #5	$59.72	11.490%	$66.5818	$66.58	$66.60	$66.60
Purchase #6	$38.36	4.134%	$39.9458	$39.95	$39.95	$39.90
Purchase #7	$231.98	10.234%	$255.7208	$255.72	$255.70	$255.70
7 purchase totals =	$767.45		$823.9990	$824.00	$824.00	$823.90