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	$116.98	6.111%	$124.1286	$124.13	$124.15	$124.10
Purchase #2	$68.69	13.635%	$78.0559	$78.06	$78.05	$78.10
Purchase #3	$122.85	7.769%	$132.3942	$132.39	$132.40	$132.40
Purchase #4	$61.83	4.455%	$64.5845	$64.58	$64.60	$64.60
Purchase #5	$24.95	8.238%	$27.0054	$27.01	$27.00	$27.00
Purchase #6	$177.34	12.799%	$200.0377	$200.04	$200.05	$200.00
Purchase #7	$102.31	6.585%	$109.0471	$109.05	$109.05	$109.00
7 purchase totals =	$674.95		$735.2534	$735.26	$735.30	$735.20