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 $131.77   8.566%   $143.0574   $143.06   $143.05   $143.10  
  Purchase #2 $85.98   6.191%   $91.303   $91.30   $91.30   $91.30  
  Purchase #3 $161.91   10.384%   $178.7227   $178.72   $178.70   $178.70  
  Purchase #4 $158.31   7.294%   $169.8571   $169.86   $169.85   $169.90  
  Purchase #5 $75.49   11.175%   $83.926   $83.93   $83.95   $83.90  
  Purchase #6 $248.92   4.724%   $260.679   $260.68   $260.70   $260.70  
  Purchase #7 $129.40   4.637%   $135.4003   $135.40   $135.40   $135.40  
  7 purchase totals = $991.78       $1,062.9455   $1,062.95   $1,062.95   $1,063.00