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	$41.34	10.183%	$45.5497	$45.55	$45.55	$45.50
Purchase #2	$208.68	4.630%	$218.3419	$218.34	$218.35	$218.30
Purchase #3	$177.86	10.435%	$196.4197	$196.42	$196.40	$196.40
Purchase #4	$80.38	5.852%	$85.0838	$85.08	$85.10	$85.10
Purchase #5	$78.37	3.663%	$81.2407	$81.24	$81.25	$81.20
Purchase #6	$224.83	8.145%	$243.1424	$243.14	$243.15	$243.10
Purchase #7	$107.88	5.375%	$113.6786	$113.68	$113.70	$113.70
7 purchase totals =	$919.34		$983.4568	$983.45	$983.50	$983.30