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	$199.89	10.863%	$221.6041	$221.60	$221.60	$221.60
Purchase #2	$148.47	11.436%	$165.449	$165.45	$165.45	$165.40
Purchase #3	$165.45	10.490%	$182.8057	$182.81	$182.80	$182.80
Purchase #4	$71.59	13.217%	$81.0521	$81.05	$81.05	$81.10
Purchase #5	$80.57	12.217%	$90.4132	$90.41	$90.40	$90.40
Purchase #6	$168.44	12.169%	$188.9375	$188.94	$188.95	$188.90
Purchase #7	$31.74	13.242%	$35.943	$35.94	$35.95	$35.90
7 purchase totals =	$866.15		$966.2046	$966.20	$966.20	$966.10