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	$169.62	13.539%	$192.5849	$192.58	$192.60	$192.60
Purchase #2	$43.39	10.398%	$47.9017	$47.90	$47.90	$47.90
Purchase #3	$210.34	8.556%	$228.3367	$228.34	$228.35	$228.30
Purchase #4	$143.54	4.852%	$150.5046	$150.50	$150.50	$150.50
Purchase #5	$131.29	10.527%	$145.1109	$145.11	$145.10	$145.10
Purchase #6	$83.50	10.850%	$92.5598	$92.56	$92.55	$92.60
Purchase #7	$35.44	8.627%	$38.4974	$38.50	$38.50	$38.50
7 purchase totals =	$817.12		$895.4960	$895.49	$895.50	$895.50