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 $59.54   3.625%   $61.6983   $61.70   $61.70   $61.70  
  Purchase #2 $229.73   10.270%   $253.3233   $253.32   $253.30   $253.30  
  Purchase #3 $62.96   13.698%   $71.5843   $71.58   $71.60   $71.60  
  Purchase #4 $217.75   9.295%   $237.9899   $237.99   $238.00   $238.00  
  Purchase #5 $154.55   9.796%   $169.6897   $169.69   $169.70   $169.70  
  Purchase #6 $181.34   12.232%   $203.5215   $203.52   $203.50   $203.50  
  Purchase #7 $49.66   8.162%   $53.7132   $53.71   $53.70   $53.70  
  7 purchase totals = $955.53       $1,051.5202   $1,051.51   $1,051.50   $1,051.50