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 $88.93   5.757%   $94.0497   $94.05   $94.05   $94.00  
  Purchase #2 $86.90   11.282%   $96.7041   $96.70   $96.70   $96.70  
  Purchase #3 $219.83   7.498%   $236.3129   $236.31   $236.30   $236.30  
  Purchase #4 $61.41   6.656%   $65.4974   $65.50   $65.50   $65.50  
  Purchase #5 $89.85   12.535%   $101.1127   $101.11   $101.10   $101.10  
  Purchase #6 $55.65   11.447%   $62.0203   $62.02   $62.00   $62.00  
  Purchase #7 $217.88   12.107%   $244.2587   $244.26   $244.25   $244.30  
  7 purchase totals = $820.45       $899.9558   $899.95   $899.90   $899.90