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	$118.59	3.151%	$122.3268	$122.33	$122.35	$122.30
Purchase #2	$73.88	12.647%	$83.2236	$83.22	$83.20	$83.20
Purchase #3	$125.51	7.140%	$134.4714	$134.47	$134.45	$134.50
Purchase #4	$82.50	13.630%	$93.7448	$93.74	$93.75	$93.70
Purchase #5	$172.56	5.811%	$182.5875	$182.59	$182.60	$182.60
Purchase #6	$89.38	11.386%	$99.5568	$99.56	$99.55	$99.60
Purchase #7	$43.38	10.316%	$47.8551	$47.86	$47.85	$47.90
7 purchase totals =	$705.80		$763.7660	$763.77	$763.75	$763.80