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 $60.73   11.450%   $67.6836   $67.68   $67.70   $67.70  
  Purchase #2 $203.66   10.380%   $224.7999   $224.80   $224.80   $224.80  
  Purchase #3 $209.73   11.367%   $233.57   $233.57   $233.55   $233.60  
  Purchase #4 $146.85   6.427%   $156.288   $156.29   $156.30   $156.30  
  Purchase #5 $106.59   10.529%   $117.8129   $117.81   $117.80   $117.80  
  Purchase #6 $239.87   6.727%   $256.0061   $256.01   $256.00   $256.00  
  Purchase #7 $129.65   12.863%   $146.3269   $146.33   $146.35   $146.30  
  7 purchase totals = $1,097.08       $1,202.4874   $1,202.49   $1,202.50   $1,202.50