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 $53.25   8.848%   $57.9616   $57.96   $57.95   $58.00  
  Purchase #2 $164.40   6.201%   $174.5944   $174.59   $174.60   $174.60  
  Purchase #3 $160.96   6.467%   $171.3693   $171.37   $171.35   $171.40  
  Purchase #4 $204.28   4.562%   $213.5993   $213.60   $213.60   $213.60  
  Purchase #5 $64.28   3.607%   $66.5986   $66.60   $66.60   $66.60  
  Purchase #6 $222.91   10.499%   $246.3133   $246.31   $246.30   $246.30  
  Purchase #7 $34.84   11.182%   $38.7358   $38.74   $38.75   $38.70  
  7 purchase totals = $904.92       $969.1723   $969.17   $969.15   $969.20