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	$33.25	5.392%	$35.0428	$35.04	$35.05	$35.00
Purchase #2	$132.47	6.853%	$141.5482	$141.55	$141.55	$141.50
Purchase #3	$63.49	9.849%	$69.7431	$69.74	$69.75	$69.70
Purchase #4	$181.51	10.529%	$200.6212	$200.62	$200.60	$200.60
Purchase #5	$77.89	4.439%	$81.3475	$81.35	$81.35	$81.30
Purchase #6	$229.35	10.869%	$254.2781	$254.28	$254.30	$254.30
Purchase #7	$227.53	12.301%	$255.5185	$255.52	$255.50	$255.50
7 purchase totals =	$945.49		$1,038.0994	$1,038.10	$1,038.10	$1,037.90