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	$209.93	11.710%	$234.5128	$234.51	$234.50	$234.50
Purchase #2	$168.64	13.870%	$192.0304	$192.03	$192.05	$192.00
Purchase #3	$87.45	3.354%	$90.3831	$90.38	$90.40	$90.40
Purchase #4	$215.67	11.694%	$240.8904	$240.89	$240.90	$240.90
Purchase #5	$135.97	8.144%	$147.0434	$147.04	$147.05	$147.00
Purchase #6	$103.85	7.243%	$111.3719	$111.37	$111.35	$111.40
Purchase #7	$117.91	7.189%	$126.3865	$126.39	$126.40	$126.40
7 purchase totals =	$1,039.42		$1,142.6185	$1,142.61	$1,142.65	$1,142.60