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	$131.96	10.582%	$145.924	$145.92	$145.90	$145.90
Purchase #2	$54.66	8.359%	$59.229	$59.23	$59.25	$59.20
Purchase #3	$191.45	5.184%	$201.3748	$201.37	$201.35	$201.40
Purchase #4	$32.92	11.104%	$36.5754	$36.58	$36.60	$36.60
Purchase #5	$18.96	3.472%	$19.6183	$19.62	$19.60	$19.60
Purchase #6	$223.88	12.737%	$252.3956	$252.40	$252.40	$252.40
Purchase #7	$40.49	4.794%	$42.4311	$42.43	$42.45	$42.40
7 purchase totals =	$694.32		$757.5482	$757.55	$757.55	$757.50