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	$196.37	10.315%	$216.6256	$216.63	$216.65	$216.60
Purchase #2	$126.76	7.578%	$136.3659	$136.37	$136.35	$136.40
Purchase #3	$172.38	4.698%	$180.4784	$180.48	$180.50	$180.50
Purchase #4	$143.95	3.134%	$148.4614	$148.46	$148.45	$148.50
Purchase #5	$35.73	9.487%	$39.1197	$39.12	$39.10	$39.10
Purchase #6	$103.57	9.389%	$113.2942	$113.29	$113.30	$113.30
Purchase #7	$229.61	11.257%	$255.4572	$255.46	$255.45	$255.50
7 purchase totals =	$1,008.37		$1,089.8024	$1,089.81	$1,089.80	$1,089.90