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 $94.73   13.150%   $107.187   $107.19   $107.20   $107.20  
  Purchase #2 $127.36   11.345%   $141.809   $141.81   $141.80   $141.80  
  Purchase #3 $43.98   12.589%   $49.5166   $49.52   $49.50   $49.50  
  Purchase #4 $97.72   12.280%   $109.72   $109.72   $109.70   $109.70  
  Purchase #5 $66.50   10.177%   $73.2677   $73.27   $73.25   $73.30  
  Purchase #6 $200.87   13.646%   $228.2807   $228.28   $228.30   $228.30  
  Purchase #7 $241.68   6.416%   $257.1862   $257.19   $257.20   $257.20  
  7 purchase totals = $872.84       $966.9672   $966.98   $966.95   $967.00