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	$212.52	13.164%	$240.4961	$240.50	$240.50	$240.50
Purchase #2	$204.97	11.508%	$228.5579	$228.56	$228.55	$228.60
Purchase #3	$41.40	13.629%	$47.0424	$47.04	$47.05	$47.00
Purchase #4	$133.42	4.849%	$139.8895	$139.89	$139.90	$139.90
Purchase #5	$92.86	12.481%	$104.4499	$104.45	$104.45	$104.40
Purchase #6	$187.79	8.582%	$203.9061	$203.91	$203.90	$203.90
Purchase #7	$136.93	8.321%	$148.3239	$148.32	$148.30	$148.30
7 purchase totals =	$1,009.89		$1,112.6658	$1,112.67	$1,112.65	$1,112.60