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 $121.38   3.545%   $125.6829   $125.68   $125.70   $125.70  
  Purchase #2 $67.55   8.229%   $73.1087   $73.11   $73.10   $73.10  
  Purchase #3 $150.29   4.840%   $157.564   $157.56   $157.55   $157.60  
  Purchase #4 $233.77   4.155%   $243.4831   $243.48   $243.50   $243.50  
  Purchase #5 $50.48   3.760%   $52.378   $52.38   $52.40   $52.40  
  Purchase #6 $228.35   9.499%   $250.041   $250.04   $250.05   $250.00  
  Purchase #7 $224.82   13.162%   $254.4108   $254.41   $254.40   $254.40  
  7 purchase totals = $1,076.64       $1,156.6685   $1,156.66   $1,156.70   $1,156.70