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	$144.37	8.704%	$156.936	$156.94	$156.95	$156.90
Purchase #2	$206.98	7.487%	$222.4766	$222.48	$222.50	$222.50
Purchase #3	$103.61	9.137%	$113.0768	$113.08	$113.10	$113.10
Purchase #4	$213.27	12.789%	$240.5451	$240.55	$240.55	$240.50
Purchase #5	$73.32	11.832%	$81.9952	$82.00	$82.00	$82.00
Purchase #6	$86.27	7.792%	$92.9922	$92.99	$93.00	$93.00
Purchase #7	$32.86	12.588%	$36.9964	$37.00	$37.00	$37.00
7 purchase totals =	$860.68		$945.0183	$945.04	$945.10	$945.00