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	$216.55	10.778%	$239.8898	$239.89	$239.90	$239.90
Purchase #2	$69.48	10.374%	$76.6879	$76.69	$76.70	$76.70
Purchase #3	$56.31	5.262%	$59.273	$59.27	$59.25	$59.30
Purchase #4	$241.71	7.510%	$259.8624	$259.86	$259.85	$259.90
Purchase #5	$104.76	4.365%	$109.3328	$109.33	$109.35	$109.30
Purchase #6	$198.41	12.828%	$223.862	$223.86	$223.85	$223.90
Purchase #7	$127.78	11.204%	$142.0965	$142.10	$142.10	$142.10
7 purchase totals =	$1,015.00		$1,111.0044	$1,111.00	$1,111.00	$1,111.10