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 $86.90   8.126%   $93.9615   $93.96   $93.95   $94.00  
  Purchase #2 $173.84   10.768%   $192.5591   $192.56   $192.55   $192.60  
  Purchase #3 $198.27   7.847%   $213.8282   $213.83   $213.85   $213.80  
  Purchase #4 $154.80   13.132%   $175.1283   $175.13   $175.15   $175.10  
  Purchase #5 $245.48   10.551%   $271.3806   $271.38   $271.40   $271.40  
  Purchase #6 $181.95   6.817%   $194.3535   $194.35   $194.35   $194.40  
  Purchase #7 $205.81   12.587%   $231.7153   $231.72   $231.70   $231.70  
  7 purchase totals = $1,247.05       $1,372.9265   $1,372.93   $1,372.95   $1,373.00