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 $84.56   11.777%   $94.5186   $94.52   $94.50   $94.50  
  Purchase #2 $38.38   8.614%   $41.6861   $41.69   $41.70   $41.70  
  Purchase #3 $216.87   7.440%   $233.0051   $233.01   $233.00   $233.00  
  Purchase #4 $147.29   4.253%   $153.5542   $153.55   $153.55   $153.60  
  Purchase #5 $204.66   4.507%   $213.884   $213.88   $213.90   $213.90  
  Purchase #6 $185.91   12.262%   $208.7063   $208.71   $208.70   $208.70  
  Purchase #7 $140.74   8.464%   $152.6522   $152.65   $152.65   $152.70  
  7 purchase totals = $1,018.41       $1,098.0065   $1,098.01   $1,098.00   $1,098.10