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	$234.26	5.490%	$247.1209	$247.12	$247.10	$247.10
Purchase #2	$113.71	11.392%	$126.6638	$126.66	$126.65	$126.70
Purchase #3	$223.47	13.719%	$254.1278	$254.13	$254.15	$254.10
Purchase #4	$71.50	13.134%	$80.8908	$80.89	$80.90	$80.90
Purchase #5	$24.38	5.698%	$25.7692	$25.77	$25.75	$25.80
Purchase #6	$151.79	4.712%	$158.9423	$158.94	$158.95	$158.90
Purchase #7	$199.89	11.596%	$223.0692	$223.07	$223.05	$223.10
7 purchase totals =	$1,019.00		$1,116.5840	$1,116.58	$1,116.55	$1,116.60