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	$94.33	4.379%	$98.4607	$98.46	$98.45	$98.50
Purchase #2	$113.50	5.276%	$119.4883	$119.49	$119.50	$119.50
Purchase #3	$7.39	10.756%	$8.1849	$8.18	$8.20	$8.20
Purchase #4	$69.65	12.692%	$78.49	$78.49	$78.50	$78.50
Purchase #5	$136.53	7.714%	$147.0619	$147.06	$147.05	$147.10
Purchase #6	$169.45	7.708%	$182.5112	$182.51	$182.50	$182.50
Purchase #7	$72.41	13.644%	$82.2896	$82.29	$82.30	$82.30
7 purchase totals =	$663.26		$716.4866	$716.48	$716.50	$716.60