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 $43.47   11.371%   $48.413   $48.41   $48.40   $48.40  
  Purchase #2 $129.42   3.499%   $133.9484   $133.95   $133.95   $133.90  
  Purchase #3 $150.53   13.490%   $170.8365   $170.84   $170.85   $170.80  
  Purchase #4 $237.54   9.277%   $259.5766   $259.58   $259.60   $259.60  
  Purchase #5 $197.82   12.266%   $222.0846   $222.08   $222.10   $222.10  
  Purchase #6 $224.73   4.552%   $234.9597   $234.96   $234.95   $235.00  
  Purchase #7 $88.63   9.118%   $96.7113   $96.71   $96.70   $96.70  
  7 purchase totals = $1,072.14       $1,166.5301   $1,166.53   $1,166.55   $1,166.50