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 $173.25   5.371%   $182.5553   $182.56   $182.55   $182.60  
  Purchase #2 $51.37   8.771%   $55.8757   $55.88   $55.90   $55.90  
  Purchase #3 $215.66   10.619%   $238.5609   $238.56   $238.55   $238.60  
  Purchase #4 $203.25   5.587%   $214.6056   $214.61   $214.60   $214.60  
  Purchase #5 $202.50   8.797%   $220.3139   $220.31   $220.30   $220.30  
  Purchase #6 $182.54   11.828%   $204.1308   $204.13   $204.15   $204.10  
  Purchase #7 $230.57   12.280%   $258.884   $258.88   $258.90   $258.90  
  7 purchase totals = $1,259.14       $1,374.9262   $1,374.93   $1,374.95   $1,375.00