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 $177.62   9.577%   $194.6307   $194.63   $194.65   $194.60  
  Purchase #2 $243.93   8.314%   $264.2103   $264.21   $264.20   $264.20  
  Purchase #3 $119.48   12.168%   $134.0183   $134.02   $134.00   $134.00  
  Purchase #4 $173.58   4.828%   $181.9604   $181.96   $181.95   $182.00  
  Purchase #5 $113.49   10.153%   $125.0126   $125.01   $125.00   $125.00  
  Purchase #6 $232.73   4.290%   $242.7141   $242.71   $242.70   $242.70  
  Purchase #7 $149.30   9.232%   $163.0834   $163.08   $163.10   $163.10  
  7 purchase totals = $1,210.13       $1,305.6298   $1,305.62   $1,305.60   $1,305.60