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	$56.52	5.380%	$59.5608	$59.56	$59.55	$59.60
Purchase #2	$10.85	8.184%	$11.738	$11.74	$11.75	$11.70
Purchase #3	$200.90	10.473%	$221.9403	$221.94	$221.95	$221.90
Purchase #4	$107.92	4.327%	$112.5897	$112.59	$112.60	$112.60
Purchase #5	$229.79	10.713%	$254.4074	$254.41	$254.40	$254.40
Purchase #6	$33.68	9.540%	$36.8931	$36.89	$36.90	$36.90
Purchase #7	$69.32	4.507%	$72.4443	$72.44	$72.45	$72.40
7 purchase totals =	$708.98		$769.5736	$769.57	$769.60	$769.50