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 $176.70   11.433%   $196.9021   $196.90   $196.90   $196.90  
  Purchase #2 $211.99   3.746%   $219.9311   $219.93   $219.95   $219.90  
  Purchase #3 $36.70   13.825%   $41.7738   $41.77   $41.75   $41.80  
  Purchase #4 $144.67   11.523%   $161.3403   $161.34   $161.35   $161.30  
  Purchase #5 $119.26   12.199%   $133.8085   $133.81   $133.80   $133.80  
  Purchase #6 $129.58   8.189%   $140.1913   $140.19   $140.20   $140.20  
  Purchase #7 $152.32   9.492%   $166.7782   $166.78   $166.80   $166.80  
  7 purchase totals = $971.22       $1,060.7253   $1,060.72   $1,060.75   $1,060.70