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 $86.30   10.301%   $95.1898   $95.19   $95.20   $95.20  
  Purchase #2 $203.92   9.755%   $223.8124   $223.81   $223.80   $223.80  
  Purchase #3 $55.46   7.575%   $59.6611   $59.66   $59.65   $59.70  
  Purchase #4 $84.97   12.686%   $95.7493   $95.75   $95.75   $95.70  
  Purchase #5 $120.70   9.176%   $131.7754   $131.78   $131.80   $131.80  
  Purchase #6 $219.85   12.790%   $247.9688   $247.97   $247.95   $248.00  
  Purchase #7 $163.58   6.650%   $174.4581   $174.46   $174.45   $174.50  
  7 purchase totals = $934.78       $1,028.6149   $1,028.62   $1,028.60   $1,028.70