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 $32.36   3.677%   $33.5499   $33.55   $33.55   $33.50  
  Purchase #2 $169.82   7.340%   $182.2848   $182.28   $182.30   $182.30  
  Purchase #3 $230.72   3.516%   $238.8321   $238.83   $238.85   $238.80  
  Purchase #4 $186.86   13.588%   $212.2505   $212.25   $212.25   $212.30  
  Purchase #5 $125.53   6.755%   $134.0096   $134.01   $134.00   $134.00  
  Purchase #6 $119.46   5.658%   $126.219   $126.22   $126.20   $126.20  
  Purchase #7 $198.64   4.808%   $208.1906   $208.19   $208.20   $208.20  
  7 purchase totals = $1,063.39       $1,135.3365   $1,135.33   $1,135.35   $1,135.30