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 $147.78   3.296%   $152.6508   $152.65   $152.65   $152.70  
  Purchase #2 $167.90   10.779%   $185.9979   $186.00   $186.00   $186.00  
  Purchase #3 $119.81   5.487%   $126.384   $126.38   $126.40   $126.40  
  Purchase #4 $169.60   13.835%   $193.0642   $193.06   $193.05   $193.10  
  Purchase #5 $189.72   5.397%   $199.9592   $199.96   $199.95   $200.00  
  Purchase #6 $123.33   13.603%   $140.1066   $140.11   $140.10   $140.10  
  Purchase #7 $191.68   7.122%   $205.3314   $205.33   $205.35   $205.30  
  7 purchase totals = $1,109.82       $1,203.4941   $1,203.49   $1,203.50   $1,203.60