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	$244.54	9.119%	$266.8396	$266.84	$266.85	$266.80
Purchase #2	$214.75	13.393%	$243.5115	$243.51	$243.50	$243.50
Purchase #3	$232.56	5.498%	$245.3461	$245.35	$245.35	$245.30
Purchase #4	$190.54	12.222%	$213.8278	$213.83	$213.85	$213.80
Purchase #5	$66.86	4.556%	$69.9061	$69.91	$69.90	$69.90
Purchase #6	$170.85	11.638%	$190.7335	$190.73	$190.75	$190.70
Purchase #7	$187.99	4.504%	$196.4571	$196.46	$196.45	$196.50
7 purchase totals =	$1,308.09		$1,426.6217	$1,426.63	$1,426.65	$1,426.50