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	$78.72	4.732%	$82.445	$82.45	$82.45	$82.40
Purchase #2	$19.99	6.570%	$21.3033	$21.30	$21.30	$21.30
Purchase #3	$114.69	10.313%	$126.518	$126.52	$126.50	$126.50
Purchase #4	$177.96	7.442%	$191.2038	$191.20	$191.20	$191.20
Purchase #5	$144.35	13.847%	$164.3381	$164.34	$164.35	$164.30
Purchase #6	$139.95	9.840%	$153.7211	$153.72	$153.70	$153.70
Purchase #7	$147.61	9.595%	$161.7732	$161.77	$161.75	$161.80
7 purchase totals =	$823.27		$901.3025	$901.30	$901.25	$901.20