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 $169.49   5.454%   $178.734   $178.73   $178.75   $178.70  
  Purchase #2 $124.83   6.848%   $133.3784   $133.38   $133.40   $133.40  
  Purchase #3 $213.89   6.785%   $228.4024   $228.40   $228.40   $228.40  
  Purchase #4 $64.93   9.310%   $70.975   $70.98   $71.00   $71.00  
  Purchase #5 $223.55   6.535%   $238.159   $238.16   $238.15   $238.20  
  Purchase #6 $88.89   6.638%   $94.7905   $94.79   $94.80   $94.80  
  Purchase #7 $61.43   6.609%   $65.4899   $65.49   $65.50   $65.50  
  7 purchase totals = $947.01       $1,009.9292   $1,009.93   $1,010.00   $1,010.00