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	$78.92	9.633%	$86.5224	$86.52	$86.50	$86.50
Purchase #2	$57.53	9.294%	$62.8768	$62.88	$62.90	$62.90
Purchase #3	$237.84	3.638%	$246.4926	$246.49	$246.50	$246.50
Purchase #4	$247.30	12.118%	$277.2678	$277.27	$277.25	$277.30
Purchase #5	$36.83	12.863%	$41.5674	$41.57	$41.55	$41.60
Purchase #6	$121.86	5.292%	$128.3088	$128.31	$128.30	$128.30
Purchase #7	$35.56	11.119%	$39.5139	$39.51	$39.50	$39.50
7 purchase totals =	$815.84		$882.5497	$882.55	$882.50	$882.60