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	$204.50	13.172%	$231.4367	$231.44	$231.45	$231.40
Purchase #2	$155.87	8.264%	$168.7511	$168.75	$168.75	$168.80
Purchase #3	$17.63	6.660%	$18.8042	$18.80	$18.80	$18.80
Purchase #4	$121.70	10.421%	$134.3824	$134.38	$134.40	$134.40
Purchase #5	$163.38	13.474%	$185.3938	$185.39	$185.40	$185.40
Purchase #6	$96.56	3.254%	$99.7021	$99.70	$99.70	$99.70
Purchase #7	$102.93	10.158%	$113.3856	$113.39	$113.40	$113.40
7 purchase totals =	$862.57		$951.8559	$951.85	$951.90	$951.90