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	$204.83	11.570%	$228.5288	$228.53	$228.55	$228.50
Purchase #2	$205.39	12.788%	$231.6553	$231.66	$231.65	$231.70
Purchase #3	$95.56	10.511%	$105.6043	$105.60	$105.60	$105.60
Purchase #4	$35.78	3.445%	$37.0126	$37.01	$37.00	$37.00
Purchase #5	$145.53	5.242%	$153.1587	$153.16	$153.15	$153.20
Purchase #6	$52.57	11.275%	$58.4973	$58.50	$58.50	$58.50
Purchase #7	$91.86	6.678%	$97.9944	$97.99	$98.00	$98.00
7 purchase totals =	$831.52		$912.4514	$912.45	$912.45	$912.50