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	$215.26	12.374%	$241.8963	$241.90	$241.90	$241.90
Purchase #2	$145.49	6.214%	$154.5307	$154.53	$154.55	$154.50
Purchase #3	$55.55	10.827%	$61.5644	$61.56	$61.55	$61.60
Purchase #4	$168.46	10.603%	$186.3218	$186.32	$186.30	$186.30
Purchase #5	$9.61	9.789%	$10.5507	$10.55	$10.55	$10.60
Purchase #6	$242.37	13.294%	$274.5907	$274.59	$274.60	$274.60
Purchase #7	$47.43	9.655%	$52.0094	$52.01	$52.00	$52.00
7 purchase totals =	$884.17		$981.4640	$981.46	$981.45	$981.50