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 $145.28   5.288%   $152.9624   $152.96   $152.95   $153.00  
  Purchase #2 $68.52   4.254%   $71.4348   $71.43   $71.45   $71.40  
  Purchase #3 $240.59   12.112%   $269.7303   $269.73   $269.75   $269.70  
  Purchase #4 $158.29   4.735%   $165.785   $165.79   $165.80   $165.80  
  Purchase #5 $224.50   12.474%   $252.5041   $252.50   $252.50   $252.50  
  Purchase #6 $162.91   8.778%   $177.2102   $177.21   $177.20   $177.20  
  Purchase #7 $153.36   9.409%   $167.7896   $167.79   $167.80   $167.80  
  7 purchase totals = $1,153.45       $1,257.4164   $1,257.41   $1,257.45   $1,257.40