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 $62.86   9.840%   $69.0454   $69.05   $69.05   $69.00  
  Purchase #2 $189.89   12.342%   $213.3262   $213.33   $213.35   $213.30  
  Purchase #3 $248.99   7.134%   $266.7529   $266.75   $266.75   $266.80  
  Purchase #4 $149.51   6.869%   $159.7798   $159.78   $159.80   $159.80  
  Purchase #5 $174.90   10.790%   $193.7717   $193.77   $193.75   $193.80  
  Purchase #6 $96.81   5.601%   $102.2323   $102.23   $102.25   $102.20  
  Purchase #7 $132.25   11.435%   $147.3728   $147.37   $147.35   $147.40  
  7 purchase totals = $1,055.21       $1,152.2811   $1,152.28   $1,152.30   $1,152.30