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 $151.41   7.681%   $163.0398   $163.04   $163.05   $163.00  
  Purchase #2 $233.46   13.662%   $265.3553   $265.36   $265.35   $265.40  
  Purchase #3 $102.86   7.704%   $110.7843   $110.78   $110.80   $110.80  
  Purchase #4 $174.76   4.191%   $182.0842   $182.08   $182.10   $182.10  
  Purchase #5 $12.70   5.847%   $13.4426   $13.44   $13.45   $13.40  
  Purchase #6 $196.89   6.589%   $209.8631   $209.86   $209.85   $209.90  
  Purchase #7 $152.67   5.196%   $160.6027   $160.60   $160.60   $160.60  
  7 purchase totals = $1,024.75       $1,105.1720   $1,105.16   $1,105.20   $1,105.20