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	$221.27	5.693%	$233.8669	$233.87	$233.85	$233.90
Purchase #2	$143.51	11.857%	$160.526	$160.53	$160.55	$160.50
Purchase #3	$18.78	10.165%	$20.689	$20.69	$20.70	$20.70
Purchase #4	$223.86	3.229%	$231.0884	$231.09	$231.10	$231.10
Purchase #5	$232.88	3.299%	$240.5627	$240.56	$240.55	$240.60
Purchase #6	$40.37	13.337%	$45.7541	$45.75	$45.75	$45.80
Purchase #7	$11.98	13.223%	$13.5641	$13.56	$13.55	$13.60
7 purchase totals =	$892.65		$946.0512	$946.05	$946.05	$946.20