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	$90.83	8.105%	$98.1918	$98.19	$98.20	$98.20
Purchase #2	$78.51	3.293%	$81.0953	$81.10	$81.10	$81.10
Purchase #3	$239.38	11.623%	$267.2031	$267.20	$267.20	$267.20
Purchase #4	$150.66	3.697%	$156.2299	$156.23	$156.25	$156.20
Purchase #5	$197.65	12.401%	$222.1606	$222.16	$222.15	$222.20
Purchase #6	$38.64	3.208%	$39.8796	$39.88	$39.90	$39.90
Purchase #7	$190.40	9.274%	$208.0577	$208.06	$208.05	$208.10
7 purchase totals =	$986.07		$1,072.8180	$1,072.82	$1,072.85	$1,072.90