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	$147.61	8.188%	$159.6963	$159.70	$159.70	$159.70
Purchase #2	$38.36	11.568%	$42.7975	$42.80	$42.80	$42.80
Purchase #3	$123.32	13.401%	$139.8461	$139.85	$139.85	$139.80
Purchase #4	$224.91	9.448%	$246.1595	$246.16	$246.15	$246.20
Purchase #5	$144.59	8.340%	$156.6488	$156.65	$156.65	$156.60
Purchase #6	$91.67	7.111%	$98.1887	$98.19	$98.20	$98.20
Purchase #7	$70.48	11.683%	$78.7142	$78.71	$78.70	$78.70
7 purchase totals =	$840.94		$922.0511	$922.06	$922.05	$922.00