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	$213.36	6.666%	$227.5826	$227.58	$227.60	$227.60
Purchase #2	$22.63	3.499%	$23.4218	$23.42	$23.40	$23.40
Purchase #3	$187.26	4.704%	$196.0687	$196.07	$196.05	$196.10
Purchase #4	$95.51	5.675%	$100.9302	$100.93	$100.95	$100.90
Purchase #5	$200.68	6.479%	$213.6821	$213.68	$213.70	$213.70
Purchase #6	$67.62	5.103%	$71.0706	$71.07	$71.05	$71.10
Purchase #7	$76.50	8.300%	$82.8495	$82.85	$82.85	$82.80
7 purchase totals =	$863.56		$915.6055	$915.60	$915.60	$915.60