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	$167.44	10.802%	$185.5269	$185.53	$185.55	$185.50
Purchase #2	$117.56	6.819%	$125.5764	$125.58	$125.60	$125.60
Purchase #3	$111.51	6.424%	$118.6734	$118.67	$118.65	$118.70
Purchase #4	$121.66	8.520%	$132.0254	$132.03	$132.05	$132.00
Purchase #5	$85.32	6.430%	$90.8061	$90.81	$90.80	$90.80
Purchase #6	$38.82	10.775%	$43.0029	$43.00	$43.00	$43.00
Purchase #7	$242.77	9.479%	$265.7822	$265.78	$265.80	$265.80
7 purchase totals =	$885.08		$961.3933	$961.40	$961.45	$961.40