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	$77.25	8.543%	$83.8495	$83.85	$83.85	$83.80
Purchase #2	$16.54	13.824%	$18.8265	$18.83	$18.85	$18.80
Purchase #3	$36.74	10.679%	$40.6635	$40.66	$40.65	$40.70
Purchase #4	$81.42	11.467%	$90.7564	$90.76	$90.75	$90.80
Purchase #5	$164.92	13.733%	$187.5685	$187.57	$187.55	$187.60
Purchase #6	$42.92	3.417%	$44.3866	$44.39	$44.40	$44.40
Purchase #7	$91.67	11.604%	$102.3074	$102.31	$102.30	$102.30
7 purchase totals =	$511.46		$568.3584	$568.37	$568.35	$568.40