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 $162.38   9.330%   $177.5301   $177.53   $177.55   $177.50  
  Purchase #2 $216.89   6.577%   $231.1549   $231.15   $231.15   $231.20  
  Purchase #3 $139.96   4.452%   $146.191   $146.19   $146.20   $146.20  
  Purchase #4 $43.99   3.146%   $45.3739   $45.37   $45.35   $45.40  
  Purchase #5 $44.32   4.245%   $46.2014   $46.20   $46.20   $46.20  
  Purchase #6 $120.64   5.233%   $126.9531   $126.95   $126.95   $127.00  
  Purchase #7 $53.27   11.873%   $59.5947   $59.59   $59.60   $59.60  
  7 purchase totals = $781.45       $832.9991   $832.98   $833.00   $833.10