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 $61.95   10.165%   $68.2472   $68.25   $68.25   $68.20  
  Purchase #2 $11.66   4.505%   $12.1853   $12.19   $12.20   $12.20  
  Purchase #3 $59.65   8.128%   $64.4984   $64.50   $64.50   $64.50  
  Purchase #4 $86.96   7.718%   $93.6716   $93.67   $93.65   $93.70  
  Purchase #5 $201.87   6.133%   $214.2507   $214.25   $214.25   $214.30  
  Purchase #6 $138.91   4.591%   $145.2874   $145.29   $145.30   $145.30  
  Purchase #7 $179.87   5.134%   $189.1045   $189.10   $189.10   $189.10  
  7 purchase totals = $740.87       $787.2451   $787.25   $787.25   $787.30