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	$115.47	9.473%	$126.4085	$126.41	$126.40	$126.40
Purchase #2	$51.85	7.429%	$55.7019	$55.70	$55.70	$55.70
Purchase #3	$32.55	3.131%	$33.5691	$33.57	$33.55	$33.60
Purchase #4	$243.74	12.802%	$274.9436	$274.94	$274.95	$274.90
Purchase #5	$187.50	4.566%	$196.0613	$196.06	$196.05	$196.10
Purchase #6	$59.25	7.771%	$63.8543	$63.85	$63.85	$63.90
Purchase #7	$208.91	8.613%	$226.9034	$226.90	$226.90	$226.90
7 purchase totals =	$899.27		$977.4421	$977.43	$977.40	$977.50