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	$146.95	10.129%	$161.8346	$161.83	$161.85	$161.80
Purchase #2	$106.71	4.872%	$111.9089	$111.91	$111.90	$111.90
Purchase #3	$75.31	4.229%	$78.4949	$78.49	$78.50	$78.50
Purchase #4	$83.69	4.345%	$87.3263	$87.33	$87.35	$87.30
Purchase #5	$31.94	12.747%	$36.0114	$36.01	$36.00	$36.00
Purchase #6	$17.75	4.391%	$18.5294	$18.53	$18.55	$18.50
Purchase #7	$133.54	13.441%	$151.4891	$151.49	$151.50	$151.50
7 purchase totals =	$595.89		$645.5946	$645.59	$645.65	$645.50