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	$89.34	11.116%	$99.271	$99.27	$99.25	$99.30
Purchase #2	$233.89	5.575%	$246.9294	$246.93	$246.95	$246.90
Purchase #3	$215.44	8.554%	$233.8687	$233.87	$233.85	$233.90
Purchase #4	$224.71	13.724%	$255.5492	$255.55	$255.55	$255.50
Purchase #5	$63.67	7.296%	$68.3154	$68.32	$68.30	$68.30
Purchase #6	$79.81	12.189%	$89.538	$89.54	$89.55	$89.50
Purchase #7	$186.69	10.487%	$206.2682	$206.27	$206.25	$206.30
7 purchase totals =	$1,093.55		$1,199.7399	$1,199.75	$1,199.70	$1,199.70