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	$175.81	5.234%	$185.0119	$185.01	$185.00	$185.00
Purchase #2	$224.51	13.855%	$255.6159	$255.62	$255.60	$255.60
Purchase #3	$213.73	9.211%	$233.4167	$233.42	$233.40	$233.40
Purchase #4	$185.90	13.118%	$210.2864	$210.29	$210.30	$210.30
Purchase #5	$87.92	7.793%	$94.7716	$94.77	$94.75	$94.80
Purchase #6	$243.38	13.516%	$276.2752	$276.28	$276.30	$276.30
Purchase #7	$127.46	13.309%	$144.4237	$144.42	$144.40	$144.40
7 purchase totals =	$1,258.71		$1,399.8014	$1,399.81	$1,399.75	$1,399.80