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 $69.86   8.817%   $76.0196   $76.02   $76.00   $76.00  
  Purchase #2 $247.65   11.690%   $276.6003   $276.60   $276.60   $276.60  
  Purchase #3 $210.44   3.787%   $218.4094   $218.41   $218.40   $218.40  
  Purchase #4 $131.84   9.566%   $144.4518   $144.45   $144.45   $144.50  
  Purchase #5 $81.95   6.669%   $87.4152   $87.42   $87.40   $87.40  
  Purchase #6 $210.67   13.533%   $239.18   $239.18   $239.20   $239.20  
  Purchase #7 $213.53   3.496%   $220.995   $221.00   $221.00   $221.00  
  7 purchase totals = $1,165.94       $1,263.0713   $1,263.08   $1,263.05   $1,263.10