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	$31.55	3.754%	$32.7344	$32.73	$32.75	$32.70
Purchase #2	$63.65	12.633%	$71.6909	$71.69	$71.70	$71.70
Purchase #3	$165.77	4.177%	$172.6942	$172.69	$172.70	$172.70
Purchase #4	$175.90	11.648%	$196.3888	$196.39	$196.40	$196.40
Purchase #5	$110.34	8.580%	$119.8072	$119.81	$119.80	$119.80
Purchase #6	$113.87	12.120%	$127.671	$127.67	$127.65	$127.70
Purchase #7	$36.79	12.167%	$41.2662	$41.27	$41.25	$41.30
7 purchase totals =	$697.87		$762.2527	$762.25	$762.25	$762.30