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	$73.47	10.749%	$81.3673	$81.37	$81.35	$81.40
Purchase #2	$247.44	8.124%	$267.542	$267.54	$267.55	$267.50
Purchase #3	$34.85	8.619%	$37.8537	$37.85	$37.85	$37.90
Purchase #4	$29.65	6.443%	$31.5603	$31.56	$31.55	$31.60
Purchase #5	$249.32	6.403%	$265.284	$265.28	$265.30	$265.30
Purchase #6	$49.94	11.499%	$55.6826	$55.68	$55.70	$55.70
Purchase #7	$249.82	6.320%	$265.6086	$265.61	$265.60	$265.60
7 purchase totals =	$934.49		$1,004.8985	$1,004.89	$1,004.90	$1,005.00