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	$221.56	4.531%	$231.5989	$231.60	$231.60	$231.60
Purchase #2	$237.88	7.668%	$256.1206	$256.12	$256.10	$256.10
Purchase #3	$28.88	9.348%	$31.5797	$31.58	$31.60	$31.60
Purchase #4	$124.62	4.860%	$130.6765	$130.68	$130.70	$130.70
Purchase #5	$192.86	12.518%	$217.0022	$217.00	$217.00	$217.00
Purchase #6	$168.53	6.222%	$179.0159	$179.02	$179.00	$179.00
Purchase #7	$102.46	8.757%	$111.4324	$111.43	$111.45	$111.40
7 purchase totals =	$1,076.79		$1,157.4262	$1,157.43	$1,157.45	$1,157.40