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 $114.42   10.589%   $126.5359   $126.54   $126.55   $126.50  
  Purchase #2 $142.78   13.461%   $161.9996   $162.00   $162.00   $162.00  
  Purchase #3 $197.72   3.507%   $204.654   $204.65   $204.65   $204.70  
  Purchase #4 $235.32   9.489%   $257.6495   $257.65   $257.65   $257.60  
  Purchase #5 $113.31   6.627%   $120.8191   $120.82   $120.80   $120.80  
  Purchase #6 $60.61   7.661%   $65.2533   $65.25   $65.25   $65.30  
  Purchase #7 $111.25   4.209%   $115.9325   $115.93   $115.95   $115.90  
  7 purchase totals = $975.41       $1,052.8439   $1,052.84   $1,052.85   $1,052.80