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 $91.60   3.542%   $94.8445   $94.84   $94.85   $94.80  
  Purchase #2 $42.50   13.391%   $48.1912   $48.19   $48.20   $48.20  
  Purchase #3 $234.78   9.670%   $257.4832   $257.48   $257.50   $257.50  
  Purchase #4 $177.36   13.714%   $201.6832   $201.68   $201.70   $201.70  
  Purchase #5 $168.65   11.868%   $188.6654   $188.67   $188.65   $188.70  
  Purchase #6 $65.63   8.506%   $71.2125   $71.21   $71.20   $71.20  
  Purchase #7 $147.99   6.179%   $157.1343   $157.13   $157.15   $157.10  
  7 purchase totals = $928.51       $1,019.2143   $1,019.20   $1,019.25   $1,019.20