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	$113.29	13.645%	$128.7484	$128.75	$128.75	$128.70
Purchase #2	$219.88	5.752%	$232.5275	$232.53	$232.55	$232.50
Purchase #3	$48.53	4.734%	$50.8274	$50.83	$50.85	$50.80
Purchase #4	$219.53	5.435%	$231.4615	$231.46	$231.45	$231.50
Purchase #5	$216.83	11.770%	$242.3509	$242.35	$242.35	$242.40
Purchase #6	$168.29	7.188%	$180.3867	$180.39	$180.40	$180.40
Purchase #7	$75.59	3.256%	$78.0512	$78.05	$78.05	$78.10
7 purchase totals =	$1,061.94		$1,144.3536	$1,144.36	$1,144.40	$1,144.40