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	$78.62	10.144%	$86.5952	$86.60	$86.60	$86.60
Purchase #2	$105.77	8.348%	$114.5997	$114.60	$114.60	$114.60
Purchase #3	$100.44	11.844%	$112.3361	$112.34	$112.35	$112.30
Purchase #4	$248.37	9.548%	$272.0844	$272.08	$272.10	$272.10
Purchase #5	$185.89	3.238%	$191.9091	$191.91	$191.90	$191.90
Purchase #6	$199.93	10.663%	$221.2485	$221.25	$221.25	$221.20
Purchase #7	$148.61	12.298%	$166.8861	$166.89	$166.90	$166.90
7 purchase totals =	$1,067.63		$1,165.6591	$1,165.67	$1,165.70	$1,165.60