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	$42.80	11.818%	$47.8581	$47.86	$47.85	$47.90
Purchase #2	$26.75	4.701%	$28.0075	$28.01	$28.00	$28.00
Purchase #3	$86.51	10.111%	$95.257	$95.26	$95.25	$95.30
Purchase #4	$92.81	8.312%	$100.5244	$100.52	$100.50	$100.50
Purchase #5	$38.81	9.516%	$42.5032	$42.50	$42.50	$42.50
Purchase #6	$155.34	6.147%	$164.8887	$164.89	$164.90	$164.90
Purchase #7	$185.35	6.161%	$196.7694	$196.77	$196.75	$196.80
7 purchase totals =	$628.37		$675.8083	$675.81	$675.75	$675.90