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	$225.95	6.768%	$241.2423	$241.24	$241.25	$241.20
Purchase #2	$181.52	10.678%	$200.9027	$200.90	$200.90	$200.90
Purchase #3	$237.54	10.494%	$262.4674	$262.47	$262.45	$262.50
Purchase #4	$12.77	7.445%	$13.7207	$13.72	$13.70	$13.70
Purchase #5	$218.35	11.365%	$243.1655	$243.17	$243.15	$243.20
Purchase #6	$80.78	3.723%	$83.7874	$83.79	$83.80	$83.80
Purchase #7	$89.81	12.832%	$101.3344	$101.33	$101.35	$101.30
7 purchase totals =	$1,046.72		$1,146.6204	$1,146.62	$1,146.60	$1,146.60