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	$171.51	10.558%	$189.618	$189.62	$189.60	$189.60
Purchase #2	$204.37	13.324%	$231.6003	$231.60	$231.60	$231.60
Purchase #3	$209.93	6.770%	$224.1423	$224.14	$224.15	$224.10
Purchase #4	$226.89	5.540%	$239.4597	$239.46	$239.45	$239.50
Purchase #5	$208.38	12.238%	$233.8815	$233.88	$233.90	$233.90
Purchase #6	$218.38	3.239%	$225.4533	$225.45	$225.45	$225.50
Purchase #7	$55.98	6.698%	$59.7295	$59.73	$59.75	$59.70
7 purchase totals =	$1,295.44		$1,403.8846	$1,403.88	$1,403.90	$1,403.90