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	$204.46	10.283%	$225.4846	$225.48	$225.50	$225.50
Purchase #2	$96.36	9.632%	$105.6414	$105.64	$105.65	$105.60
Purchase #3	$154.67	8.652%	$168.052	$168.05	$168.05	$168.10
Purchase #4	$152.55	10.301%	$168.2642	$168.26	$168.25	$168.30
Purchase #5	$218.81	8.527%	$237.4679	$237.47	$237.45	$237.50
Purchase #6	$164.29	12.515%	$184.8509	$184.85	$184.85	$184.90
Purchase #7	$105.25	4.347%	$109.8252	$109.83	$109.85	$109.80
7 purchase totals =	$1,096.39		$1,199.5862	$1,199.58	$1,199.60	$1,199.70