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 $62.35   12.613%   $70.2142   $70.21   $70.20   $70.20  
  Purchase #2 $118.83   5.815%   $125.74   $125.74   $125.75   $125.70  
  Purchase #3 $15.64   9.294%   $17.0936   $17.09   $17.10   $17.10  
  Purchase #4 $222.42   9.463%   $243.4676   $243.47   $243.45   $243.50  
  Purchase #5 $243.94   6.576%   $259.9815   $259.98   $260.00   $260.00  
  Purchase #6 $221.88   12.210%   $248.9715   $248.97   $248.95   $249.00  
  Purchase #7 $218.30   8.707%   $237.3074   $237.31   $237.30   $237.30  
  7 purchase totals = $1,103.36       $1,202.7758   $1,202.77   $1,202.75   $1,202.80