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 $90.78   3.495%   $93.9528   $93.95   $93.95   $94.00  
  Purchase #2 $57.45   8.611%   $62.397   $62.40   $62.40   $62.40  
  Purchase #3 $174.91   5.630%   $184.7574   $184.76   $184.75   $184.80  
  Purchase #4 $195.25   7.300%   $209.5033   $209.50   $209.50   $209.50  
  Purchase #5 $246.39   12.425%   $277.004   $277.00   $277.00   $277.00  
  Purchase #6 $39.70   9.689%   $43.5465   $43.55   $43.55   $43.50  
  Purchase #7 $183.71   6.261%   $195.2121   $195.21   $195.20   $195.20  
  7 purchase totals = $988.19       $1,066.3731   $1,066.37   $1,066.35   $1,066.40