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 $35.95   6.267%   $38.203   $38.20   $38.20   $38.20  
  Purchase #2 $173.63   4.396%   $181.2628   $181.26   $181.25   $181.30  
  Purchase #3 $167.61   5.351%   $176.5788   $176.58   $176.60   $176.60  
  Purchase #4 $147.89   13.531%   $167.901   $167.90   $167.90   $167.90  
  Purchase #5 $64.26   5.298%   $67.6645   $67.66   $67.65   $67.70  
  Purchase #6 $145.66   6.388%   $154.9648   $154.96   $154.95   $155.00  
  Purchase #7 $204.36   10.203%   $225.2109   $225.21   $225.20   $225.20  
  7 purchase totals = $939.36       $1,011.7858   $1,011.77   $1,011.75   $1,011.90