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 $108.28   7.189%   $116.0642   $116.06   $116.05   $116.10  
  Purchase #2 $235.93   11.771%   $263.7013   $263.70   $263.70   $263.70  
  Purchase #3 $158.39   9.637%   $173.654   $173.65   $173.65   $173.70  
  Purchase #4 $221.47   7.812%   $238.7712   $238.77   $238.75   $238.80  
  Purchase #5 $112.93   5.112%   $118.703   $118.70   $118.70   $118.70  
  Purchase #6 $218.54   5.601%   $230.7804   $230.78   $230.80   $230.80  
  Purchase #7 $63.57   4.558%   $66.4675   $66.47   $66.45   $66.50  
  7 purchase totals = $1,119.11       $1,208.1416   $1,208.13   $1,208.10   $1,208.30