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	$44.68	8.123%	$48.3094	$48.31	$48.30	$48.30
Purchase #2	$32.39	4.246%	$33.7653	$33.77	$33.75	$33.80
Purchase #3	$213.72	8.483%	$231.8499	$231.85	$231.85	$231.80
Purchase #4	$90.41	5.812%	$95.6646	$95.66	$95.65	$95.70
Purchase #5	$159.41	5.285%	$167.8348	$167.83	$167.85	$167.80
Purchase #6	$76.37	7.822%	$82.3437	$82.34	$82.35	$82.30
Purchase #7	$83.46	4.478%	$87.1973	$87.20	$87.20	$87.20
7 purchase totals =	$700.44		$746.9650	$746.96	$746.95	$746.90