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	$91.38	11.380%	$101.779	$101.78	$101.80	$101.80
Purchase #2	$236.67	11.491%	$263.8657	$263.87	$263.85	$263.90
Purchase #3	$34.99	13.582%	$39.7423	$39.74	$39.75	$39.70
Purchase #4	$207.84	12.522%	$233.8657	$233.87	$233.85	$233.90
Purchase #5	$12.46	6.187%	$13.2309	$13.23	$13.25	$13.20
Purchase #6	$114.45	8.155%	$123.7834	$123.78	$123.80	$123.80
Purchase #7	$88.91	11.859%	$99.4538	$99.45	$99.45	$99.50
7 purchase totals =	$786.70		$875.7208	$875.72	$875.75	$875.80