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	$105.93	7.462%	$113.8345	$113.83	$113.85	$113.80
Purchase #2	$120.74	8.475%	$130.9727	$130.97	$130.95	$131.00
Purchase #3	$178.68	7.739%	$192.508	$192.51	$192.50	$192.50
Purchase #4	$37.72	10.806%	$41.796	$41.80	$41.80	$41.80
Purchase #5	$80.46	11.626%	$89.8143	$89.81	$89.80	$89.80
Purchase #6	$203.94	12.724%	$229.8893	$229.89	$229.90	$229.90
Purchase #7	$32.76	4.223%	$34.1435	$34.14	$34.15	$34.10
7 purchase totals =	$760.23		$832.9583	$832.95	$832.95	$832.90