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 $218.57   7.616%   $235.2163   $235.22   $235.20   $235.20  
  Purchase #2 $55.57   9.777%   $61.0031   $61.00   $61.00   $61.00  
  Purchase #3 $191.57   12.752%   $215.999   $216.00   $216.00   $216.00  
  Purchase #4 $187.80   7.338%   $201.5808   $201.58   $201.60   $201.60  
  Purchase #5 $174.46   7.729%   $187.944   $187.94   $187.95   $187.90  
  Purchase #6 $203.38   7.114%   $217.8485   $217.85   $217.85   $217.80  
  Purchase #7 $242.94   7.272%   $260.6066   $260.61   $260.60   $260.60  
  7 purchase totals = $1,274.29       $1,380.1983   $1,380.20   $1,380.20   $1,380.10