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 $84.69   9.464%   $92.7051   $92.71   $92.70   $92.70  
  Purchase #2 $195.41   12.438%   $219.7151   $219.72   $219.70   $219.70  
  Purchase #3 $65.67   4.220%   $68.4413   $68.44   $68.45   $68.40  
  Purchase #4 $80.61   8.424%   $87.4006   $87.40   $87.40   $87.40  
  Purchase #5 $200.39   9.131%   $218.6876   $218.69   $218.70   $218.70  
  Purchase #6 $247.80   5.304%   $260.9433   $260.94   $260.95   $260.90  
  Purchase #7 $129.70   12.637%   $146.0902   $146.09   $146.10   $146.10  
  7 purchase totals = $1,004.27       $1,093.9832   $1,093.99   $1,094.00   $1,093.90