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 $58.94   5.267%   $62.0444   $62.04   $62.05   $62.00  
  Purchase #2 $82.66   4.106%   $86.054   $86.05   $86.05   $86.10  
  Purchase #3 $23.76   4.624%   $24.8587   $24.86   $24.85   $24.90  
  Purchase #4 $100.40   9.170%   $109.6067   $109.61   $109.60   $109.60  
  Purchase #5 $148.66   5.608%   $156.9969   $157.00   $157.00   $157.00  
  Purchase #6 $99.61   8.776%   $108.3518   $108.35   $108.35   $108.40  
  Purchase #7 $216.84   5.423%   $228.5992   $228.60   $228.60   $228.60  
  7 purchase totals = $730.87       $776.5117   $776.51   $776.50   $776.60