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 $56.64   10.762%   $62.7356   $62.74   $62.75   $62.70  
  Purchase #2 $228.50   6.302%   $242.9001   $242.90   $242.90   $242.90  
  Purchase #3 $98.54   9.761%   $108.1585   $108.16   $108.15   $108.20  
  Purchase #4 $230.56   7.520%   $247.8981   $247.90   $247.90   $247.90  
  Purchase #5 $6.71   4.595%   $7.0183   $7.02   $7.00   $7.00  
  Purchase #6 $247.73   13.164%   $280.3412   $280.34   $280.35   $280.30  
  Purchase #7 $204.81   10.336%   $225.9792   $225.98   $226.00   $226.00  
  7 purchase totals = $1,073.49       $1,175.0310   $1,175.04   $1,175.05   $1,175.00