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	$170.67	11.838%	$190.8739	$190.87	$190.85	$190.90
Purchase #2	$87.72	9.724%	$96.2499	$96.25	$96.25	$96.20
Purchase #3	$177.51	11.755%	$198.3763	$198.38	$198.40	$198.40
Purchase #4	$129.61	8.126%	$140.1421	$140.14	$140.15	$140.10
Purchase #5	$63.41	4.402%	$66.2013	$66.20	$66.20	$66.20
Purchase #6	$35.54	11.268%	$39.5446	$39.54	$39.55	$39.50
Purchase #7	$63.71	12.197%	$71.4807	$71.48	$71.50	$71.50
7 purchase totals =	$728.17		$802.8688	$802.86	$802.90	$802.80