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 $56.81   10.118%   $62.558   $62.56   $62.55   $62.60  
  Purchase #2 $162.43   5.260%   $170.9738   $170.97   $170.95   $171.00  
  Purchase #3 $152.69   3.357%   $157.8158   $157.82   $157.80   $157.80  
  Purchase #4 $195.92   12.699%   $220.7999   $220.80   $220.80   $220.80  
  Purchase #5 $20.51   8.402%   $22.2333   $22.23   $22.25   $22.20  
  Purchase #6 $204.94   7.247%   $219.792   $219.79   $219.80   $219.80  
  Purchase #7 $227.67   9.191%   $248.5951   $248.60   $248.60   $248.60  
  7 purchase totals = $1,020.97       $1,102.7679   $1,102.77   $1,102.75   $1,102.80