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 $57.41   5.425%   $60.5245   $60.52   $60.50   $60.50  
  Purchase #2 $11.54   13.184%   $13.0614   $13.06   $13.05   $13.10  
  Purchase #3 $166.75   5.661%   $176.1897   $176.19   $176.20   $176.20  
  Purchase #4 $69.50   4.130%   $72.3704   $72.37   $72.35   $72.40  
  Purchase #5 $170.96   5.139%   $179.7456   $179.75   $179.75   $179.70  
  Purchase #6 $200.55   5.467%   $211.5141   $211.51   $211.50   $211.50  
  Purchase #7 $230.52   4.356%   $240.5615   $240.56   $240.55   $240.60  
  7 purchase totals = $907.23       $953.9672   $953.96   $953.90   $954.00