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	$83.66	3.540%	$86.6216	$86.62	$86.60	$86.60
Purchase #2	$84.47	10.343%	$93.2067	$93.21	$93.20	$93.20
Purchase #3	$121.90	9.858%	$133.9169	$133.92	$133.90	$133.90
Purchase #4	$155.44	11.189%	$172.8322	$172.83	$172.85	$172.80
Purchase #5	$177.92	10.489%	$196.582	$196.58	$196.60	$196.60
Purchase #6	$135.69	12.431%	$152.5576	$152.56	$152.55	$152.60
Purchase #7	$193.51	9.860%	$212.5901	$212.59	$212.60	$212.60
7 purchase totals =	$952.59		$1,048.3071	$1,048.31	$1,048.30	$1,048.30