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	$55.31	12.766%	$62.3709	$62.37	$62.35	$62.40
Purchase #2	$75.86	3.271%	$78.3414	$78.34	$78.35	$78.30
Purchase #3	$134.95	13.715%	$153.4584	$153.46	$153.45	$153.50
Purchase #4	$163.72	7.278%	$175.6355	$175.64	$175.65	$175.60
Purchase #5	$240.69	5.329%	$253.5164	$253.52	$253.50	$253.50
Purchase #6	$184.66	8.667%	$200.6645	$200.66	$200.65	$200.70
Purchase #7	$146.97	13.595%	$166.9506	$166.95	$166.95	$167.00
7 purchase totals =	$1,002.16		$1,090.9377	$1,090.94	$1,090.90	$1,091.00