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	$248.65	13.602%	$282.4714	$282.47	$282.45	$282.50
Purchase #2	$85.98	13.710%	$97.7679	$97.77	$97.75	$97.80
Purchase #3	$168.70	4.290%	$175.9372	$175.94	$175.95	$175.90
Purchase #4	$74.65	4.264%	$77.8331	$77.83	$77.85	$77.80
Purchase #5	$55.58	7.661%	$59.838	$59.84	$59.85	$59.80
Purchase #6	$190.38	11.413%	$212.1081	$212.11	$212.10	$212.10
Purchase #7	$61.65	12.762%	$69.5178	$69.52	$69.50	$69.50
7 purchase totals =	$885.59		$975.4735	$975.48	$975.45	$975.40