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	$49.34	13.399%	$55.9511	$55.95	$55.95	$56.00
Purchase #2	$37.59	11.375%	$41.8659	$41.87	$41.85	$41.90
Purchase #3	$42.86	13.189%	$48.5128	$48.51	$48.50	$48.50
Purchase #4	$216.33	3.241%	$223.3413	$223.34	$223.35	$223.30
Purchase #5	$236.52	13.677%	$268.8688	$268.87	$268.85	$268.90
Purchase #6	$165.46	12.759%	$186.571	$186.57	$186.55	$186.60
Purchase #7	$246.94	5.161%	$259.6846	$259.68	$259.70	$259.70
7 purchase totals =	$995.04		$1,084.7955	$1,084.79	$1,084.75	$1,084.90