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 $194.29   4.453%   $202.9417   $202.94   $202.95   $202.90  
  Purchase #2 $9.69   10.365%   $10.6944   $10.69   $10.70   $10.70  
  Purchase #3 $181.46   3.659%   $188.0996   $188.10   $188.10   $188.10  
  Purchase #4 $158.29   11.635%   $176.707   $176.71   $176.70   $176.70  
  Purchase #5 $8.79   9.763%   $9.6482   $9.65   $9.65   $9.60  
  Purchase #6 $168.57   6.820%   $180.0665   $180.07   $180.05   $180.10  
  Purchase #7 $220.95   9.480%   $241.8961   $241.90   $241.90   $241.90  
  7 purchase totals = $942.04       $1,010.0535   $1,010.06   $1,010.05   $1,010.00