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 $58.68   6.442%   $62.4602   $62.46   $62.45   $62.50  
  Purchase #2 $216.75   6.577%   $231.0056   $231.01   $231.00   $231.00  
  Purchase #3 $249.65   13.574%   $283.5375   $283.54   $283.55   $283.50  
  Purchase #4 $35.36   10.826%   $39.1881   $39.19   $39.20   $39.20  
  Purchase #5 $146.37   12.834%   $165.1551   $165.16   $165.15   $165.20  
  Purchase #6 $236.65   3.450%   $244.8144   $244.81   $244.80   $244.80  
  Purchase #7 $228.70   3.656%   $237.0613   $237.06   $237.05   $237.10  
  7 purchase totals = $1,172.16       $1,263.2222   $1,263.23   $1,263.20   $1,263.30