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 $68.71   10.640%   $76.0207   $76.02   $76.00   $76.00  
  Purchase #2 $46.84   11.820%   $52.3765   $52.38   $52.40   $52.40  
  Purchase #3 $232.37   8.690%   $252.563   $252.56   $252.55   $252.60  
  Purchase #4 $153.77   10.145%   $169.37   $169.37   $169.35   $169.40  
  Purchase #5 $177.42   6.589%   $189.1102   $189.11   $189.10   $189.10  
  Purchase #6 $117.89   5.807%   $124.7359   $124.74   $124.75   $124.70  
  Purchase #7 $234.97   10.357%   $259.3058   $259.31   $259.30   $259.30  
  7 purchase totals = $1,031.97       $1,123.4821   $1,123.49   $1,123.45   $1,123.50