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 $38.26   9.605%   $41.9349   $41.93   $41.95   $41.90  
  Purchase #2 $236.86   13.116%   $267.9266   $267.93   $267.95   $267.90  
  Purchase #3 $190.35   6.138%   $202.0337   $202.03   $202.05   $202.00  
  Purchase #4 $80.35   8.713%   $87.3509   $87.35   $87.35   $87.40  
  Purchase #5 $231.95   6.264%   $246.4793   $246.48   $246.50   $246.50  
  Purchase #6 $238.26   12.632%   $268.357   $268.36   $268.35   $268.40  
  Purchase #7 $189.80   11.127%   $210.919   $210.92   $210.90   $210.90  
  7 purchase totals = $1,205.83       $1,325.0014   $1,325.00   $1,325.05   $1,325.00