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	$144.71	7.810%	$156.0119	$156.01	$156.00	$156.00
Purchase #2	$57.71	10.189%	$63.5901	$63.59	$63.60	$63.60
Purchase #3	$156.83	7.218%	$168.15	$168.15	$168.15	$168.20
Purchase #4	$25.46	10.295%	$28.0811	$28.08	$28.10	$28.10
Purchase #5	$116.71	12.178%	$130.9229	$130.92	$130.90	$130.90
Purchase #6	$35.84	12.139%	$40.1906	$40.19	$40.20	$40.20
Purchase #7	$89.83	11.435%	$100.1021	$100.10	$100.10	$100.10
7 purchase totals =	$627.09		$687.0487	$687.04	$687.05	$687.10