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 $227.75   3.605%   $235.9604   $235.96   $235.95   $236.00  
  Purchase #2 $202.48   10.635%   $224.0137   $224.01   $224.00   $224.00  
  Purchase #3 $95.64   3.564%   $99.0486   $99.05   $99.05   $99.00  
  Purchase #4 $151.89   5.478%   $160.2105   $160.21   $160.20   $160.20  
  Purchase #5 $54.93   10.608%   $60.757   $60.76   $60.75   $60.80  
  Purchase #6 $110.57   8.447%   $119.9098   $119.91   $119.90   $119.90  
  Purchase #7 $130.86   10.589%   $144.7168   $144.72   $144.70   $144.70  
  7 purchase totals = $974.12       $1,044.6168   $1,044.62   $1,044.55   $1,044.60