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	$202.25	10.727%	$223.9454	$223.95	$223.95	$223.90
Purchase #2	$246.89	10.533%	$272.8949	$272.89	$272.90	$272.90
Purchase #3	$36.51	3.705%	$37.8627	$37.86	$37.85	$37.90
Purchase #4	$60.56	6.387%	$64.428	$64.43	$64.45	$64.40
Purchase #5	$26.64	5.509%	$28.1076	$28.11	$28.10	$28.10
Purchase #6	$134.49	7.245%	$144.2338	$144.23	$144.25	$144.20
Purchase #7	$185.41	8.213%	$200.6377	$200.64	$200.65	$200.60
7 purchase totals =	$892.75		$972.1101	$972.11	$972.15	$972.00