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 $195.95   4.769%   $205.2949   $205.29   $205.30   $205.30  
  Purchase #2 $180.79   10.296%   $199.4041   $199.40   $199.40   $199.40  
  Purchase #3 $226.49   7.629%   $243.7689   $243.77   $243.75   $243.80  
  Purchase #4 $128.54   8.745%   $139.7808   $139.78   $139.80   $139.80  
  Purchase #5 $186.45   7.290%   $200.0422   $200.04   $200.05   $200.00  
  Purchase #6 $93.40   6.206%   $99.1964   $99.20   $99.20   $99.20  
  Purchase #7 $154.67   12.215%   $173.5629   $173.56   $173.55   $173.60  
  7 purchase totals = $1,166.29       $1,261.0502   $1,261.04   $1,261.05   $1,261.10