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 $52.97   9.414%   $57.9566   $57.96   $57.95   $58.00  
  Purchase #2 $199.40   8.510%   $216.3689   $216.37   $216.35   $216.40  
  Purchase #3 $111.70   9.814%   $122.6622   $122.66   $122.65   $122.70  
  Purchase #4 $132.50   7.234%   $142.0851   $142.09   $142.10   $142.10  
  Purchase #5 $184.77   6.704%   $197.157   $197.16   $197.15   $197.20  
  Purchase #6 $59.98   5.517%   $63.2891   $63.29   $63.30   $63.30  
  Purchase #7 $204.40   10.632%   $226.1318   $226.13   $226.15   $226.10  
  7 purchase totals = $945.72       $1,025.6507   $1,025.66   $1,025.65   $1,025.80