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	$139.93	5.351%	$147.4177	$147.42	$147.40	$147.40
Purchase #2	$98.71	12.855%	$111.3992	$111.40	$111.40	$111.40
Purchase #3	$6.80	11.215%	$7.5626	$7.56	$7.55	$7.60
Purchase #4	$137.49	10.396%	$151.7835	$151.78	$151.80	$151.80
Purchase #5	$28.63	7.527%	$30.785	$30.79	$30.80	$30.80
Purchase #6	$172.50	7.468%	$185.3823	$185.38	$185.40	$185.40
Purchase #7	$227.83	6.444%	$242.5114	$242.51	$242.50	$242.50
7 purchase totals =	$811.89		$876.8417	$876.84	$876.85	$876.90