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	$231.49	5.443%	$244.09	$244.09	$244.10	$244.10
Purchase #2	$96.75	3.619%	$100.2514	$100.25	$100.25	$100.30
Purchase #3	$122.70	11.318%	$136.5872	$136.59	$136.60	$136.60
Purchase #4	$113.97	3.306%	$117.7378	$117.74	$117.75	$117.70
Purchase #5	$150.34	9.337%	$164.3772	$164.38	$164.40	$164.40
Purchase #6	$38.32	13.729%	$43.581	$43.58	$43.60	$43.60
Purchase #7	$26.38	4.172%	$27.4806	$27.48	$27.50	$27.50
7 purchase totals =	$779.95		$834.1052	$834.11	$834.20	$834.20