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	$102.38	8.631%	$111.2164	$111.22	$111.20	$111.20
Purchase #2	$114.85	12.741%	$129.483	$129.48	$129.50	$129.50
Purchase #3	$28.60	9.375%	$31.2813	$31.28	$31.30	$31.30
Purchase #4	$48.26	13.279%	$54.6684	$54.67	$54.65	$54.70
Purchase #5	$218.33	4.346%	$227.8186	$227.82	$227.80	$227.80
Purchase #6	$95.36	7.522%	$102.533	$102.53	$102.55	$102.50
Purchase #7	$157.95	10.264%	$174.162	$174.16	$174.15	$174.20
7 purchase totals =	$765.73		$831.1627	$831.16	$831.15	$831.20