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	$114.85	7.372%	$123.3167	$123.32	$123.30	$123.30
Purchase #2	$57.37	5.561%	$60.5603	$60.56	$60.55	$60.60
Purchase #3	$19.73	8.226%	$21.353	$21.35	$21.35	$21.40
Purchase #4	$15.61	11.184%	$17.3558	$17.36	$17.35	$17.40
Purchase #5	$36.44	12.570%	$41.0205	$41.02	$41.00	$41.00
Purchase #6	$38.94	8.360%	$42.1954	$42.20	$42.20	$42.20
Purchase #7	$117.82	12.543%	$132.5982	$132.60	$132.60	$132.60
7 purchase totals =	$400.76		$438.3999	$438.41	$438.35	$438.50