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 $71.30   5.226%   $75.0261   $75.03   $75.05   $75.00  
  Purchase #2 $224.94   8.321%   $243.6573   $243.66   $243.65   $243.70  
  Purchase #3 $159.82   8.854%   $173.9705   $173.97   $173.95   $174.00  
  Purchase #4 $201.27   9.870%   $221.1353   $221.14   $221.15   $221.10  
  Purchase #5 $109.84   7.638%   $118.2296   $118.23   $118.25   $118.20  
  Purchase #6 $202.56   12.726%   $228.3378   $228.34   $228.35   $228.30  
  Purchase #7 $232.27   6.224%   $246.7265   $246.73   $246.75   $246.70  
  7 purchase totals = $1,202.00       $1,307.0831   $1,307.10   $1,307.15   $1,307.00