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 $96.57   9.775%   $106.0097   $106.01   $106.00   $106.00  
  Purchase #2 $226.65   7.110%   $242.7648   $242.76   $242.75   $242.80  
  Purchase #3 $76.38   10.770%   $84.6061   $84.61   $84.60   $84.60  
  Purchase #4 $231.87   12.347%   $260.499   $260.50   $260.50   $260.50  
  Purchase #5 $110.99   10.519%   $122.665   $122.67   $122.65   $122.70  
  Purchase #6 $101.70   5.753%   $107.5508   $107.55   $107.55   $107.60  
  Purchase #7 $218.65   11.294%   $243.3443   $243.34   $243.35   $243.30  
  7 purchase totals = $1,062.81       $1,167.4397   $1,167.44   $1,167.40   $1,167.50