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 $243.32   7.577%   $261.7564   $261.76   $261.75   $261.80  
  Purchase #2 $226.31   5.263%   $238.2207   $238.22   $238.20   $238.20  
  Purchase #3 $40.56   11.780%   $45.338   $45.34   $45.35   $45.30  
  Purchase #4 $28.31   3.507%   $29.3028   $29.30   $29.30   $29.30  
  Purchase #5 $118.34   7.169%   $126.8238   $126.82   $126.80   $126.80  
  Purchase #6 $184.92   6.693%   $197.2967   $197.30   $197.30   $197.30  
  Purchase #7 $180.37   12.533%   $202.9758   $202.98   $203.00   $203.00  
  7 purchase totals = $1,022.13       $1,101.7142   $1,101.72   $1,101.70   $1,101.70