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 $203.43   5.859%   $215.349   $215.35   $215.35   $215.30  
  Purchase #2 $165.25   6.172%   $175.4492   $175.45   $175.45   $175.40  
  Purchase #3 $193.83   12.381%   $217.8281   $217.83   $217.85   $217.80  
  Purchase #4 $55.37   9.647%   $60.7115   $60.71   $60.70   $60.70  
  Purchase #5 $150.97   6.851%   $161.313   $161.31   $161.30   $161.30  
  Purchase #6 $36.25   11.262%   $40.3325   $40.33   $40.35   $40.30  
  Purchase #7 $42.88   7.116%   $45.9313   $45.93   $45.95   $45.90  
  7 purchase totals = $847.98       $916.9146   $916.91   $916.95   $916.70