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 $212.66   10.527%   $235.0467   $235.05   $235.05   $235.00  
  Purchase #2 $83.79   13.318%   $94.9492   $94.95   $94.95   $94.90  
  Purchase #3 $147.66   5.257%   $155.4225   $155.42   $155.40   $155.40  
  Purchase #4 $95.31   10.826%   $105.6283   $105.63   $105.65   $105.60  
  Purchase #5 $162.46   12.822%   $183.2906   $183.29   $183.30   $183.30  
  Purchase #6 $158.27   6.564%   $168.6588   $168.66   $168.65   $168.70  
  Purchase #7 $61.86   10.744%   $68.5062   $68.51   $68.50   $68.50  
  7 purchase totals = $922.01       $1,011.5023   $1,011.51   $1,011.50   $1,011.40