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	$113.86	12.233%	$127.7885	$127.79	$127.80	$127.80
Purchase #2	$82.35	4.187%	$85.798	$85.80	$85.80	$85.80
Purchase #3	$143.83	11.357%	$160.1648	$160.16	$160.15	$160.20
Purchase #4	$174.93	8.249%	$189.36	$189.36	$189.35	$189.40
Purchase #5	$104.55	3.647%	$108.3629	$108.36	$108.35	$108.40
Purchase #6	$76.56	11.761%	$85.5642	$85.56	$85.55	$85.60
Purchase #7	$114.50	5.340%	$120.6143	$120.61	$120.60	$120.60
7 purchase totals =	$810.58		$877.6527	$877.64	$877.60	$877.80