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 $173.33   10.682%   $191.8451   $191.85   $191.85   $191.80  
  Purchase #2 $239.61   7.803%   $258.3068   $258.31   $258.30   $258.30  
  Purchase #3 $241.92   9.560%   $265.0476   $265.05   $265.05   $265.00  
  Purchase #4 $177.58   13.562%   $201.6634   $201.66   $201.65   $201.70  
  Purchase #5 $162.41   8.685%   $176.5153   $176.52   $176.50   $176.50  
  Purchase #6 $52.42   12.594%   $59.0218   $59.02   $59.00   $59.00  
  Purchase #7 $48.72   11.153%   $54.1537   $54.15   $54.15   $54.20  
  7 purchase totals = $1,095.99       $1,206.5537   $1,206.56   $1,206.50   $1,206.50