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	$214.37	13.270%	$242.8169	$242.82	$242.80	$242.80
Purchase #2	$103.58	13.492%	$117.555	$117.56	$117.55	$117.60
Purchase #3	$76.30	7.499%	$82.0217	$82.02	$82.00	$82.00
Purchase #4	$241.99	13.440%	$274.5135	$274.51	$274.50	$274.50
Purchase #5	$74.30	11.650%	$82.956	$82.96	$82.95	$83.00
Purchase #6	$156.96	5.330%	$165.326	$165.33	$165.35	$165.30
Purchase #7	$85.48	7.282%	$91.7047	$91.70	$91.70	$91.70
7 purchase totals =	$952.98		$1,056.8938	$1,056.90	$1,056.85	$1,056.90