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	$6.62	3.506%	$6.8521	$6.85	$6.85	$6.90
Purchase #2	$215.81	10.231%	$237.8895	$237.89	$237.90	$237.90
Purchase #3	$237.35	7.656%	$255.5215	$255.52	$255.50	$255.50
Purchase #4	$229.95	10.411%	$253.8901	$253.89	$253.90	$253.90
Purchase #5	$129.47	12.785%	$146.0227	$146.02	$146.00	$146.00
Purchase #6	$83.64	7.528%	$89.9364	$89.94	$89.95	$89.90
Purchase #7	$22.77	6.267%	$24.197	$24.20	$24.20	$24.20
7 purchase totals =	$925.61		$1,014.3093	$1,014.31	$1,014.30	$1,014.30