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 $40.54   13.409%   $45.976   $45.98   $46.00   $46.00  
  Purchase #2 $212.43   7.144%   $227.606   $227.61   $227.60   $227.60  
  Purchase #3 $197.99   10.420%   $218.6206   $218.62   $218.60   $218.60  
  Purchase #4 $77.39   5.754%   $81.843   $81.84   $81.85   $81.80  
  Purchase #5 $228.80   11.258%   $254.5583   $254.56   $254.55   $254.60  
  Purchase #6 $49.99   4.688%   $52.3335   $52.33   $52.35   $52.30  
  Purchase #7 $119.73   13.529%   $135.9283   $135.93   $135.95   $135.90  
  7 purchase totals = $926.87       $1,016.8657   $1,016.87   $1,016.90   $1,016.80