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	$34.46	5.452%	$36.3388	$36.34	$36.35	$36.30
Purchase #2	$55.52	12.567%	$62.4972	$62.50	$62.50	$62.50
Purchase #3	$15.67	11.661%	$17.4973	$17.50	$17.50	$17.50
Purchase #4	$117.48	11.723%	$131.2522	$131.25	$131.25	$131.30
Purchase #5	$215.55	6.366%	$229.2719	$229.27	$229.25	$229.30
Purchase #6	$51.88	4.815%	$54.378	$54.38	$54.40	$54.40
Purchase #7	$73.46	9.531%	$80.4615	$80.46	$80.45	$80.50
7 purchase totals =	$564.02		$611.6969	$611.70	$611.70	$611.80