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 $212.60   11.520%   $237.0915   $237.09   $237.10   $237.10  
  Purchase #2 $182.84   8.784%   $198.9007   $198.90   $198.90   $198.90  
  Purchase #3 $204.87   4.298%   $213.6753   $213.68   $213.70   $213.70  
  Purchase #4 $58.79   12.268%   $66.0024   $66.00   $66.00   $66.00  
  Purchase #5 $163.75   11.558%   $182.6762   $182.68   $182.70   $182.70  
  Purchase #6 $151.92   10.309%   $167.5814   $167.58   $167.60   $167.60  
  Purchase #7 $133.52   3.420%   $138.0864   $138.09   $138.10   $138.10  
  7 purchase totals = $1,108.29       $1,204.0139   $1,204.02   $1,204.10   $1,204.10