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	$175.41	6.583%	$186.9572	$186.96	$186.95	$187.00
Purchase #2	$182.78	7.577%	$196.6292	$196.63	$196.65	$196.60
Purchase #3	$78.64	8.742%	$85.5147	$85.51	$85.50	$85.50
Purchase #4	$143.73	8.182%	$155.49	$155.49	$155.50	$155.50
Purchase #5	$42.83	6.183%	$45.4782	$45.48	$45.50	$45.50
Purchase #6	$15.60	11.779%	$17.4375	$17.44	$17.45	$17.40
Purchase #7	$205.76	10.671%	$227.7166	$227.72	$227.70	$227.70
7 purchase totals =	$844.75		$915.2234	$915.23	$915.25	$915.20