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	$51.97	5.681%	$54.9224	$54.92	$54.90	$54.90
Purchase #2	$32.28	3.481%	$33.4037	$33.40	$33.40	$33.40
Purchase #3	$205.39	6.676%	$219.1018	$219.10	$219.10	$219.10
Purchase #4	$37.66	6.202%	$39.9957	$40.00	$40.00	$40.00
Purchase #5	$225.80	5.566%	$238.368	$238.37	$238.35	$238.40
Purchase #6	$147.76	11.207%	$164.3195	$164.32	$164.30	$164.30
Purchase #7	$236.29	10.668%	$261.4974	$261.50	$261.50	$261.50
7 purchase totals =	$937.15		$1,011.6085	$1,011.61	$1,011.55	$1,011.60