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 $23.53   7.698%   $25.3413   $25.34   $25.35   $25.30  
  Purchase #2 $246.34   6.165%   $261.5269   $261.53   $261.55   $261.50  
  Purchase #3 $120.94   13.381%   $137.123   $137.12   $137.10   $137.10  
  Purchase #4 $112.94   10.747%   $125.0777   $125.08   $125.10   $125.10  
  Purchase #5 $205.74   9.189%   $224.6454   $224.65   $224.65   $224.60  
  Purchase #6 $160.29   9.511%   $175.5352   $175.54   $175.55   $175.50  
  Purchase #7 $225.73   11.594%   $251.9011   $251.90   $251.90   $251.90  
  7 purchase totals = $1,095.51       $1,201.1506   $1,201.16   $1,201.20   $1,201.00