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	$131.54	5.258%	$138.4564	$138.46	$138.45	$138.50
Purchase #2	$124.77	7.812%	$134.517	$134.52	$134.50	$134.50
Purchase #3	$75.95	9.234%	$82.9632	$82.96	$82.95	$83.00
Purchase #4	$218.67	5.801%	$231.355	$231.36	$231.35	$231.40
Purchase #5	$94.29	8.485%	$102.2905	$102.29	$102.30	$102.30
Purchase #6	$210.83	7.372%	$226.3724	$226.37	$226.35	$226.40
Purchase #7	$91.99	9.727%	$100.9379	$100.94	$100.95	$100.90
7 purchase totals =	$948.04		$1,016.8924	$1,016.90	$1,016.85	$1,017.00