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	$42.29	4.655%	$44.2586	$44.26	$44.25	$44.30
Purchase #2	$119.76	13.722%	$136.1935	$136.19	$136.20	$136.20
Purchase #3	$83.56	3.647%	$86.6074	$86.61	$86.60	$86.60
Purchase #4	$132.72	7.452%	$142.6103	$142.61	$142.60	$142.60
Purchase #5	$13.52	9.161%	$14.7586	$14.76	$14.75	$14.80
Purchase #6	$18.90	13.872%	$21.5218	$21.52	$21.50	$21.50
Purchase #7	$121.81	11.547%	$135.8754	$135.88	$135.90	$135.90
7 purchase totals =	$532.56		$581.8256	$581.83	$581.80	$581.90