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	$33.54	11.597%	$37.4296	$37.43	$37.45	$37.40
Purchase #2	$235.99	10.611%	$261.0309	$261.03	$261.05	$261.00
Purchase #3	$28.40	13.540%	$32.2454	$32.25	$32.25	$32.20
Purchase #4	$119.69	7.606%	$128.7936	$128.79	$128.80	$128.80
Purchase #5	$238.93	10.753%	$264.6221	$264.62	$264.60	$264.60
Purchase #6	$192.55	10.408%	$212.5906	$212.59	$212.60	$212.60
Purchase #7	$100.26	6.581%	$106.8581	$106.86	$106.85	$106.90
7 purchase totals =	$949.36		$1,043.5703	$1,043.57	$1,043.60	$1,043.50