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 $61.82   12.341%   $69.4492   $69.45   $69.45   $69.40  
  Purchase #2 $241.61   6.787%   $258.0081   $258.01   $258.00   $258.00  
  Purchase #3 $90.72   7.459%   $97.4868   $97.49   $97.50   $97.50  
  Purchase #4 $174.54   8.813%   $189.9222   $189.92   $189.90   $189.90  
  Purchase #5 $119.27   4.515%   $124.655   $124.66   $124.65   $124.70  
  Purchase #6 $212.64   3.624%   $220.3461   $220.35   $220.35   $220.30  
  Purchase #7 $171.93   9.488%   $188.2427   $188.24   $188.25   $188.20  
  7 purchase totals = $1,072.53       $1,148.1101   $1,148.12   $1,148.10   $1,148.00