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	$201.67	10.279%	$222.3997	$222.40	$222.40	$222.40
Purchase #2	$123.28	13.550%	$139.9844	$139.98	$140.00	$140.00
Purchase #3	$156.88	9.402%	$171.6299	$171.63	$171.65	$171.60
Purchase #4	$250.70	10.690%	$277.4998	$277.50	$277.50	$277.50
Purchase #5	$137.29	4.783%	$143.8566	$143.86	$143.85	$143.90
Purchase #6	$40.32	11.482%	$44.9495	$44.95	$44.95	$44.90
Purchase #7	$24.26	5.665%	$25.6343	$25.63	$25.65	$25.60
7 purchase totals =	$934.40		$1,025.9542	$1,025.95	$1,026.00	$1,025.90