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 $211.92   13.803%   $241.1713   $241.17   $241.15   $241.20  
  Purchase #2 $116.79   5.175%   $122.8339   $122.83   $122.85   $122.80  
  Purchase #3 $140.64   11.270%   $156.4901   $156.49   $156.50   $156.50  
  Purchase #4 $201.54   8.703%   $219.08   $219.08   $219.10   $219.10  
  Purchase #5 $198.94   6.275%   $211.4235   $211.42   $211.40   $211.40  
  Purchase #6 $116.57   13.574%   $132.3932   $132.39   $132.40   $132.40  
  Purchase #7 $78.91   7.682%   $84.9719   $84.97   $84.95   $85.00  
  7 purchase totals = $1,065.31       $1,168.3639   $1,168.35   $1,168.35   $1,168.40