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	$141.83	13.425%	$160.8707	$160.87	$160.85	$160.90
Purchase #2	$139.82	7.425%	$150.2016	$150.20	$150.20	$150.20
Purchase #3	$46.28	13.683%	$52.6125	$52.61	$52.60	$52.60
Purchase #4	$31.58	10.806%	$34.9925	$34.99	$35.00	$35.00
Purchase #5	$103.66	12.216%	$116.3231	$116.32	$116.30	$116.30
Purchase #6	$33.59	12.723%	$37.8637	$37.86	$37.85	$37.90
Purchase #7	$139.62	6.591%	$148.8224	$148.82	$148.80	$148.80
7 purchase totals =	$636.38		$701.6865	$701.67	$701.60	$701.70