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	$196.45	6.173%	$208.5769	$208.58	$208.60	$208.60
Purchase #2	$38.71	9.673%	$42.4544	$42.45	$42.45	$42.50
Purchase #3	$38.33	11.270%	$42.6498	$42.65	$42.65	$42.60
Purchase #4	$177.41	3.785%	$184.125	$184.13	$184.15	$184.10
Purchase #5	$22.73	13.415%	$25.7792	$25.78	$25.80	$25.80
Purchase #6	$135.97	11.661%	$151.8255	$151.83	$151.85	$151.80
Purchase #7	$117.82	11.856%	$131.7887	$131.79	$131.80	$131.80
7 purchase totals =	$727.42		$787.1995	$787.21	$787.30	$787.20