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 $212.64   9.405%   $232.6388   $232.64   $232.65   $232.60  
  Purchase #2 $180.29   13.662%   $204.9212   $204.92   $204.90   $204.90  
  Purchase #3 $190.85   10.162%   $210.2442   $210.24   $210.25   $210.20  
  Purchase #4 $186.89   5.160%   $196.5335   $196.53   $196.55   $196.50  
  Purchase #5 $34.57   4.722%   $36.2024   $36.20   $36.20   $36.20  
  Purchase #6 $36.85   13.229%   $41.7249   $41.72   $41.70   $41.70  
  Purchase #7 $125.65   13.772%   $142.9545   $142.95   $142.95   $143.00  
  7 purchase totals = $967.74       $1,065.2195   $1,065.20   $1,065.20   $1,065.10