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 $88.42   6.806%   $94.4379   $94.44   $94.45   $94.40  
  Purchase #2 $238.60   8.530%   $258.9526   $258.95   $258.95   $259.00  
  Purchase #3 $139.61   11.679%   $155.9151   $155.92   $155.90   $155.90  
  Purchase #4 $30.82   3.255%   $31.8232   $31.82   $31.80   $31.80  
  Purchase #5 $161.28   8.828%   $175.5178   $175.52   $175.50   $175.50  
  Purchase #6 $191.33   3.332%   $197.7051   $197.71   $197.70   $197.70  
  Purchase #7 $245.69   6.657%   $262.0456   $262.05   $262.05   $262.00  
  7 purchase totals = $1,095.75       $1,176.3973   $1,176.41   $1,176.35   $1,176.30