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	$64.88	4.571%	$67.8457	$67.85	$67.85	$67.80
Purchase #2	$155.90	6.408%	$165.8901	$165.89	$165.90	$165.90
Purchase #3	$125.25	5.361%	$131.9647	$131.96	$131.95	$132.00
Purchase #4	$161.41	6.372%	$171.695	$171.70	$171.70	$171.70
Purchase #5	$236.37	12.246%	$265.3159	$265.32	$265.30	$265.30
Purchase #6	$102.38	13.702%	$116.4081	$116.41	$116.40	$116.40
Purchase #7	$151.77	10.657%	$167.9441	$167.94	$167.95	$167.90
7 purchase totals =	$997.96		$1,087.0636	$1,087.07	$1,087.05	$1,087.00