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	$74.33	5.735%	$78.5928	$78.59	$78.60	$78.60
Purchase #2	$158.31	6.208%	$168.1379	$168.14	$168.15	$168.10
Purchase #3	$180.83	13.641%	$205.497	$205.50	$205.50	$205.50
Purchase #4	$240.57	9.288%	$262.9141	$262.91	$262.90	$262.90
Purchase #5	$45.45	10.792%	$50.355	$50.36	$50.35	$50.40
Purchase #6	$182.70	8.407%	$198.0596	$198.06	$198.05	$198.10
Purchase #7	$141.61	4.853%	$148.4823	$148.48	$148.50	$148.50
7 purchase totals =	$1,023.80		$1,112.0387	$1,112.04	$1,112.05	$1,112.10