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 $220.61   10.299%   $243.3306   $243.33   $243.35   $243.30  
  Purchase #2 $23.93   8.640%   $25.9976   $26.00   $26.00   $26.00  
  Purchase #3 $14.77   5.345%   $15.5595   $15.56   $15.55   $15.60  
  Purchase #4 $204.88   6.614%   $218.4308   $218.43   $218.45   $218.40  
  Purchase #5 $67.86   5.103%   $71.3229   $71.32   $71.30   $71.30  
  Purchase #6 $247.28   5.731%   $261.4516   $261.45   $261.45   $261.50  
  Purchase #7 $232.86   11.783%   $260.2979   $260.30   $260.30   $260.30  
  7 purchase totals = $1,012.19       $1,096.3909   $1,096.39   $1,096.40   $1,096.40