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 $130.85   8.373%   $141.8061   $141.81   $141.80   $141.80  
  Purchase #2 $84.43   9.727%   $92.6425   $92.64   $92.65   $92.60  
  Purchase #3 $37.60   11.425%   $41.8958   $41.90   $41.90   $41.90  
  Purchase #4 $110.78   11.262%   $123.256   $123.26   $123.25   $123.30  
  Purchase #5 $118.70   8.663%   $128.983   $128.98   $129.00   $129.00  
  Purchase #6 $158.60   5.735%   $167.6957   $167.70   $167.70   $167.70  
  Purchase #7 $64.37   8.410%   $69.7835   $69.78   $69.80   $69.80  
  7 purchase totals = $705.33       $766.0626   $766.07   $766.10   $766.10