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 $182.38   12.412%   $205.017   $205.02   $205.00   $205.00  
  Purchase #2 $202.53   7.548%   $217.817   $217.82   $217.80   $217.80  
  Purchase #3 $43.80   7.317%   $47.0048   $47.00   $47.00   $47.00  
  Purchase #4 $247.54   3.791%   $256.9242   $256.92   $256.90   $256.90  
  Purchase #5 $232.62   4.523%   $243.1414   $243.14   $243.15   $243.10  
  Purchase #6 $192.35   10.635%   $212.8064   $212.81   $212.80   $212.80  
  Purchase #7 $31.99   5.790%   $33.8422   $33.84   $33.85   $33.80  
  7 purchase totals = $1,133.21       $1,216.5530   $1,216.55   $1,216.50   $1,216.40