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	$213.67	6.185%	$226.8855	$226.89	$226.90	$226.90
Purchase #2	$74.48	5.433%	$78.5265	$78.53	$78.55	$78.50
Purchase #3	$74.75	7.720%	$80.5207	$80.52	$80.50	$80.50
Purchase #4	$181.86	8.515%	$197.3454	$197.35	$197.35	$197.30
Purchase #5	$200.34	10.755%	$221.8866	$221.89	$221.90	$221.90
Purchase #6	$233.71	9.555%	$256.041	$256.04	$256.05	$256.00
Purchase #7	$137.53	9.689%	$150.8553	$150.86	$150.85	$150.90
7 purchase totals =	$1,116.34		$1,212.0610	$1,212.08	$1,212.10	$1,212.00