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	$82.59	11.183%	$91.826	$91.83	$91.85	$91.80
Purchase #2	$237.85	6.409%	$253.0938	$253.09	$253.10	$253.10
Purchase #3	$218.35	10.854%	$242.0497	$242.05	$242.05	$242.00
Purchase #4	$17.28	8.371%	$18.7265	$18.73	$18.75	$18.70
Purchase #5	$90.72	11.655%	$101.2934	$101.29	$101.30	$101.30
Purchase #6	$68.96	4.868%	$72.317	$72.32	$72.30	$72.30
Purchase #7	$84.97	10.131%	$93.5783	$93.58	$93.60	$93.60
7 purchase totals =	$800.72		$872.8847	$872.89	$872.95	$872.80