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 $118.86   6.351%   $126.4088   $126.41   $126.40   $126.40  
  Purchase #2 $243.98   5.502%   $257.4038   $257.40   $257.40   $257.40  
  Purchase #3 $222.32   11.242%   $247.3132   $247.31   $247.30   $247.30  
  Purchase #4 $173.35   5.140%   $182.2602   $182.26   $182.25   $182.30  
  Purchase #5 $173.25   11.860%   $193.7975   $193.80   $193.80   $193.80  
  Purchase #6 $163.32   5.292%   $171.9629   $171.96   $171.95   $172.00  
  Purchase #7 $61.26   5.469%   $64.6103   $64.61   $64.60   $64.60  
  7 purchase totals = $1,156.34       $1,243.7567   $1,243.75   $1,243.70   $1,243.80