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	$205.81	5.172%	$216.4545	$216.45	$216.45	$216.50
Purchase #2	$40.72	11.611%	$45.448	$45.45	$45.45	$45.40
Purchase #3	$100.48	13.242%	$113.7856	$113.79	$113.80	$113.80
Purchase #4	$27.52	13.708%	$31.2924	$31.29	$31.30	$31.30
Purchase #5	$37.56	13.203%	$42.519	$42.52	$42.50	$42.50
Purchase #6	$103.81	3.615%	$107.5627	$107.56	$107.55	$107.60
Purchase #7	$197.52	3.490%	$204.4134	$204.41	$204.40	$204.40
7 purchase totals =	$713.42		$761.4756	$761.47	$761.45	$761.50