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 $69.70   9.547%   $76.3543   $76.35   $76.35   $76.40  
  Purchase #2 $92.69   3.175%   $95.6329   $95.63   $95.65   $95.60  
  Purchase #3 $108.52   12.288%   $121.8549   $121.85   $121.85   $121.90  
  Purchase #4 $190.84   6.485%   $203.216   $203.22   $203.20   $203.20  
  Purchase #5 $234.63   13.299%   $265.8334   $265.83   $265.85   $265.80  
  Purchase #6 $49.62   8.326%   $53.7514   $53.75   $53.75   $53.80  
  Purchase #7 $208.64   4.353%   $217.7221   $217.72   $217.70   $217.70  
  7 purchase totals = $954.64       $1,034.3650   $1,034.35   $1,034.35   $1,034.40