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 $211.38   3.605%   $219.0002   $219.00   $219.00   $219.00  
  Purchase #2 $242.55   13.501%   $275.2967   $275.30   $275.30   $275.30  
  Purchase #3 $19.63   5.172%   $20.6453   $20.65   $20.65   $20.60  
  Purchase #4 $113.38   5.379%   $119.4787   $119.48   $119.50   $119.50  
  Purchase #5 $210.77   12.385%   $236.8739   $236.87   $236.85   $236.90  
  Purchase #6 $112.61   3.732%   $116.8126   $116.81   $116.80   $116.80  
  Purchase #7 $124.89   10.474%   $137.971   $137.97   $137.95   $138.00  
  7 purchase totals = $1,035.21       $1,126.0784   $1,126.08   $1,126.05   $1,126.10