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	$166.77	9.631%	$182.8316	$182.83	$182.85	$182.80
Purchase #2	$162.33	3.501%	$168.0132	$168.01	$168.00	$168.00
Purchase #3	$113.37	10.180%	$124.9111	$124.91	$124.90	$124.90
Purchase #4	$242.38	6.735%	$258.7043	$258.70	$258.70	$258.70
Purchase #5	$138.65	11.377%	$154.4242	$154.42	$154.40	$154.40
Purchase #6	$164.57	11.543%	$183.5663	$183.57	$183.55	$183.60
Purchase #7	$134.93	6.834%	$144.1511	$144.15	$144.15	$144.20
7 purchase totals =	$1,123.00		$1,216.6018	$1,216.59	$1,216.55	$1,216.60