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 $60.25   4.171%   $62.763   $62.76   $62.75   $62.80  
  Purchase #2 $66.27   5.555%   $69.9513   $69.95   $69.95   $70.00  
  Purchase #3 $128.67   8.459%   $139.5542   $139.55   $139.55   $139.60  
  Purchase #4 $139.27   3.347%   $143.9314   $143.93   $143.95   $143.90  
  Purchase #5 $239.92   3.103%   $247.3647   $247.36   $247.35   $247.40  
  Purchase #6 $226.30   3.363%   $233.9105   $233.91   $233.90   $233.90  
  Purchase #7 $229.34   6.260%   $243.6967   $243.70   $243.70   $243.70  
  7 purchase totals = $1,090.02       $1,141.1718   $1,141.16   $1,141.15   $1,141.30