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	$75.30	13.732%	$85.6402	$85.64	$85.65	$85.60
Purchase #2	$23.43	4.465%	$24.4761	$24.48	$24.50	$24.50
Purchase #3	$177.50	5.540%	$187.3335	$187.33	$187.35	$187.30
Purchase #4	$170.29	5.637%	$179.8892	$179.89	$179.90	$179.90
Purchase #5	$27.67	4.197%	$28.8313	$28.83	$28.85	$28.80
Purchase #6	$189.85	13.504%	$215.4873	$215.49	$215.50	$215.50
Purchase #7	$29.32	11.335%	$32.6434	$32.64	$32.65	$32.60
7 purchase totals =	$693.36		$754.3010	$754.30	$754.40	$754.20