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	$10.98	3.264%	$11.3384	$11.34	$11.35	$11.30
Purchase #2	$211.29	3.577%	$218.8478	$218.85	$218.85	$218.80
Purchase #3	$153.78	4.851%	$161.2399	$161.24	$161.25	$161.20
Purchase #4	$162.85	13.233%	$184.3999	$184.40	$184.40	$184.40
Purchase #5	$134.76	11.345%	$150.0485	$150.05	$150.05	$150.00
Purchase #6	$6.70	10.712%	$7.4177	$7.42	$7.40	$7.40
Purchase #7	$6.87	10.428%	$7.5864	$7.59	$7.60	$7.60
7 purchase totals =	$687.23		$740.8786	$740.89	$740.90	$740.70