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	13.443%	$277.4135	$277.41	$277.40	$277.40
Purchase #2	$220.70	7.359%	$236.9413	$236.94	$236.95	$236.90
Purchase #3	$90.36	7.367%	$97.0168	$97.02	$97.00	$97.00
Purchase #4	$35.94	4.584%	$37.5875	$37.59	$37.60	$37.60
Purchase #5	$39.85	7.609%	$42.8822	$42.88	$42.90	$42.90
Purchase #6	$45.84	9.338%	$50.1205	$50.12	$50.10	$50.10
Purchase #7	$246.31	8.760%	$267.8868	$267.89	$267.90	$267.90
7 purchase totals =	$923.54		$1,009.8486	$1,009.85	$1,009.85	$1,009.80