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	$207.76	9.862%	$228.2493	$228.25	$228.25	$228.20
Purchase #2	$113.33	3.139%	$116.8874	$116.89	$116.90	$116.90
Purchase #3	$206.82	5.569%	$218.3378	$218.34	$218.35	$218.30
Purchase #4	$38.62	11.317%	$42.9906	$42.99	$43.00	$43.00
Purchase #5	$132.59	7.532%	$142.5767	$142.58	$142.60	$142.60
Purchase #6	$32.40	4.465%	$33.8467	$33.85	$33.85	$33.80
Purchase #7	$99.50	5.317%	$104.7904	$104.79	$104.80	$104.80
7 purchase totals =	$831.02		$887.6789	$887.69	$887.75	$887.60