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 $172.98   12.476%   $194.561   $194.56   $194.55   $194.60  
  Purchase #2 $97.58   6.840%   $104.2545   $104.25   $104.25   $104.30  
  Purchase #3 $48.59   12.548%   $54.6871   $54.69   $54.70   $54.70  
  Purchase #4 $154.38   4.253%   $160.9458   $160.95   $160.95   $160.90  
  Purchase #5 $189.57   6.221%   $201.3631   $201.36   $201.35   $201.40  
  Purchase #6 $186.74   13.623%   $212.1796   $212.18   $212.20   $212.20  
  Purchase #7 $113.73   10.672%   $125.8673   $125.87   $125.85   $125.90  
  7 purchase totals = $963.57       $1,053.8584   $1,053.86   $1,053.85   $1,054.00