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	$59.95	10.329%	$66.1422	$66.14	$66.15	$66.10
Purchase #2	$51.50	4.767%	$53.955	$53.96	$53.95	$54.00
Purchase #3	$178.87	4.266%	$186.5006	$186.50	$186.50	$186.50
Purchase #4	$119.98	11.594%	$133.8905	$133.89	$133.90	$133.90
Purchase #5	$145.44	4.874%	$152.5287	$152.53	$152.55	$152.50
Purchase #6	$190.42	4.144%	$198.311	$198.31	$198.30	$198.30
Purchase #7	$61.81	11.339%	$68.8186	$68.82	$68.80	$68.80
7 purchase totals =	$807.97		$860.1466	$860.15	$860.15	$860.10