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	$170.91	11.704%	$190.9133	$190.91	$190.90	$190.90
Purchase #2	$30.78	3.482%	$31.8518	$31.85	$31.85	$31.90
Purchase #3	$13.52	7.754%	$14.5683	$14.57	$14.55	$14.60
Purchase #4	$144.76	8.849%	$157.5698	$157.57	$157.55	$157.60
Purchase #5	$196.78	9.759%	$215.9838	$215.98	$216.00	$216.00
Purchase #6	$172.90	11.170%	$192.2129	$192.21	$192.20	$192.20
Purchase #7	$124.64	13.540%	$141.5163	$141.52	$141.50	$141.50
7 purchase totals =	$854.29		$944.6162	$944.61	$944.55	$944.70