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 $57.55   8.857%   $62.6472   $62.65   $62.65   $62.60  
  Purchase #2 $231.57   6.312%   $246.1867   $246.19   $246.20   $246.20  
  Purchase #3 $199.38   9.224%   $217.7708   $217.77   $217.75   $217.80  
  Purchase #4 $182.28   11.621%   $203.4628   $203.46   $203.45   $203.50  
  Purchase #5 $52.56   4.842%   $55.105   $55.11   $55.10   $55.10  
  Purchase #6 $163.33   11.290%   $181.77   $181.77   $181.75   $181.80  
  Purchase #7 $99.80   6.370%   $106.1573   $106.16   $106.15   $106.20  
  7 purchase totals = $986.47       $1,073.0998   $1,073.11   $1,073.05   $1,073.20