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	$192.93	3.774%	$200.2112	$200.21	$200.20	$200.20
Purchase #2	$222.96	10.659%	$246.7253	$246.73	$246.75	$246.70
Purchase #3	$230.99	10.493%	$255.2278	$255.23	$255.25	$255.20
Purchase #4	$229.61	12.600%	$258.5409	$258.54	$258.55	$258.50
Purchase #5	$77.90	6.214%	$82.7407	$82.74	$82.75	$82.70
Purchase #6	$171.59	5.506%	$181.0377	$181.04	$181.05	$181.00
Purchase #7	$160.54	7.379%	$172.3862	$172.39	$172.40	$172.40
7 purchase totals =	$1,286.52		$1,396.8698	$1,396.88	$1,396.95	$1,396.70