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	$169.37	12.521%	$190.5768	$190.58	$190.60	$190.60
Purchase #2	$97.49	5.243%	$102.6014	$102.60	$102.60	$102.60
Purchase #3	$124.61	4.622%	$130.3695	$130.37	$130.35	$130.40
Purchase #4	$195.25	6.703%	$208.3376	$208.34	$208.35	$208.30
Purchase #5	$224.42	8.196%	$242.8135	$242.81	$242.80	$242.80
Purchase #6	$239.85	6.687%	$255.8888	$255.89	$255.90	$255.90
Purchase #7	$119.32	7.478%	$128.2427	$128.24	$128.25	$128.20
7 purchase totals =	$1,170.31		$1,258.8303	$1,258.83	$1,258.85	$1,258.80