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 $42.26   10.516%   $46.7041   $46.70   $46.70   $46.70  
  Purchase #2 $103.77   11.450%   $115.6517   $115.65   $115.65   $115.70  
  Purchase #3 $248.52   13.616%   $282.3585   $282.36   $282.35   $282.40  
  Purchase #4 $179.68   4.276%   $187.3631   $187.36   $187.35   $187.40  
  Purchase #5 $95.27   10.222%   $105.0085   $105.01   $105.00   $105.00  
  Purchase #6 $232.96   5.535%   $245.8543   $245.85   $245.85   $245.90  
  Purchase #7 $198.74   12.691%   $223.9621   $223.96   $223.95   $224.00  
  7 purchase totals = $1,101.20       $1,206.9023   $1,206.89   $1,206.85   $1,207.10