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 $152.62   11.195%   $169.7058   $169.71   $169.70   $169.70  
  Purchase #2 $194.62   5.444%   $205.2151   $205.22   $205.20   $205.20  
  Purchase #3 $183.32   4.629%   $191.8059   $191.81   $191.80   $191.80  
  Purchase #4 $123.62   8.735%   $134.4182   $134.42   $134.40   $134.40  
  Purchase #5 $68.38   7.555%   $73.5461   $73.55   $73.55   $73.50  
  Purchase #6 $211.65   5.579%   $223.458   $223.46   $223.45   $223.50  
  Purchase #7 $59.92   9.218%   $65.4434   $65.44   $65.45   $65.40  
  7 purchase totals = $994.13       $1,063.5925   $1,063.61   $1,063.55   $1,063.50