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 $54.80   11.548%   $61.1283   $61.13   $61.15   $61.10  
  Purchase #2 $209.78   7.337%   $225.1716   $225.17   $225.15   $225.20  
  Purchase #3 $165.26   8.219%   $178.8427   $178.84   $178.85   $178.80  
  Purchase #4 $227.92   6.571%   $242.8966   $242.90   $242.90   $242.90  
  Purchase #5 $158.32   6.723%   $168.9639   $168.96   $168.95   $169.00  
  Purchase #6 $171.84   11.221%   $191.1222   $191.12   $191.10   $191.10  
  Purchase #7 $52.31   8.828%   $56.9279   $56.93   $56.95   $56.90  
  7 purchase totals = $1,040.23       $1,125.0532   $1,125.05   $1,125.05   $1,125.00