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 $62.33   11.411%   $69.4425   $69.44   $69.45   $69.40  
  Purchase #2 $136.57   12.407%   $153.5142   $153.51   $153.50   $153.50  
  Purchase #3 $12.72   9.326%   $13.9063   $13.91   $13.90   $13.90  
  Purchase #4 $90.73   6.820%   $96.9178   $96.92   $96.90   $96.90  
  Purchase #5 $195.45   5.507%   $206.2134   $206.21   $206.20   $206.20  
  Purchase #6 $212.37   12.112%   $238.0923   $238.09   $238.10   $238.10  
  Purchase #7 $193.67   12.108%   $217.1196   $217.12   $217.10   $217.10  
  7 purchase totals = $903.84       $995.2061   $995.20   $995.15   $995.10