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 $184.51   5.225%   $194.1506   $194.15   $194.15   $194.20  
  Purchase #2 $80.87   5.475%   $85.2976   $85.30   $85.30   $85.30  
  Purchase #3 $77.44   13.281%   $87.7248   $87.72   $87.70   $87.70  
  Purchase #4 $217.88   3.725%   $225.996   $226.00   $226.00   $226.00  
  Purchase #5 $39.34   9.682%   $43.1489   $43.15   $43.15   $43.10  
  Purchase #6 $77.55   4.187%   $80.797   $80.80   $80.80   $80.80  
  Purchase #7 $250.41   3.164%   $258.333   $258.33   $258.35   $258.30  
  7 purchase totals = $928.00       $975.4479   $975.45   $975.45   $975.40