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	$93.85	11.475%	$104.6193	$104.62	$104.60	$104.60
Purchase #2	$237.87	13.664%	$270.3726	$270.37	$270.35	$270.40
Purchase #3	$142.61	10.778%	$157.9805	$157.98	$158.00	$158.00
Purchase #4	$149.61	11.587%	$166.9453	$166.95	$166.95	$166.90
Purchase #5	$128.89	10.808%	$142.8204	$142.82	$142.80	$142.80
Purchase #6	$161.81	7.843%	$174.5008	$174.50	$174.50	$174.50
Purchase #7	$82.43	4.478%	$86.1212	$86.12	$86.10	$86.10
7 purchase totals =	$997.07		$1,103.3601	$1,103.36	$1,103.30	$1,103.30