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 $84.65   11.274%   $94.1934   $94.19   $94.20   $94.20  
  Purchase #2 $145.92   9.282%   $159.4643   $159.46   $159.45   $159.50  
  Purchase #3 $59.94   7.547%   $64.4637   $64.46   $64.45   $64.50  
  Purchase #4 $241.62   5.703%   $255.3996   $255.40   $255.40   $255.40  
  Purchase #5 $214.66   3.521%   $222.2182   $222.22   $222.20   $222.20  
  Purchase #6 $163.77   8.235%   $177.2565   $177.26   $177.25   $177.30  
  Purchase #7 $80.93   11.546%   $90.2742   $90.27   $90.25   $90.30  
  7 purchase totals = $991.49       $1,063.2699   $1,063.26   $1,063.20   $1,063.40