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	$78.29	11.627%	$87.3928	$87.39	$87.40	$87.40
Purchase #2	$92.31	7.785%	$99.4963	$99.50	$99.50	$99.50
Purchase #3	$160.37	7.605%	$172.5661	$172.57	$172.55	$172.60
Purchase #4	$239.48	9.567%	$262.3911	$262.39	$262.40	$262.40
Purchase #5	$169.63	5.734%	$179.3566	$179.36	$179.35	$179.40
Purchase #6	$32.34	13.692%	$36.768	$36.77	$36.75	$36.80
Purchase #7	$218.27	8.532%	$236.8928	$236.89	$236.90	$236.90
7 purchase totals =	$990.69		$1,074.8637	$1,074.87	$1,074.85	$1,075.00