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	$195.25	11.189%	$217.0965	$217.10	$217.10	$217.10
Purchase #2	$68.43	12.279%	$76.8325	$76.83	$76.85	$76.80
Purchase #3	$58.38	10.352%	$64.4235	$64.42	$64.40	$64.40
Purchase #4	$101.59	9.853%	$111.5997	$111.60	$111.60	$111.60
Purchase #5	$24.31	3.141%	$25.0736	$25.07	$25.05	$25.10
Purchase #6	$89.97	4.607%	$94.1149	$94.11	$94.10	$94.10
Purchase #7	$90.86	5.658%	$96.0009	$96.00	$96.00	$96.00
7 purchase totals =	$628.79		$685.1416	$685.13	$685.10	$685.10