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	$75.55	8.538%	$82.0005	$82.00	$82.00	$82.00
Purchase #2	$203.58	4.397%	$212.5314	$212.53	$212.55	$212.50
Purchase #3	$213.39	5.386%	$224.8832	$224.88	$224.90	$224.90
Purchase #4	$90.49	5.508%	$95.4742	$95.47	$95.45	$95.50
Purchase #5	$186.44	5.501%	$196.6961	$196.70	$196.70	$196.70
Purchase #6	$28.46	5.122%	$29.9177	$29.92	$29.90	$29.90
Purchase #7	$56.97	4.625%	$59.6049	$59.60	$59.60	$59.60
7 purchase totals =	$854.88		$901.1080	$901.10	$901.10	$901.10