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 $153.94   13.186%   $174.2385   $174.24   $174.25   $174.20  
  Purchase #2 $206.49   3.463%   $213.6407   $213.64   $213.65   $213.60  
  Purchase #3 $215.69   6.421%   $229.5395   $229.54   $229.55   $229.50  
  Purchase #4 $41.41   8.414%   $44.8942   $44.89   $44.90   $44.90  
  Purchase #5 $52.66   13.525%   $59.7823   $59.78   $59.80   $59.80  
  Purchase #6 $157.43   3.385%   $162.759   $162.76   $162.75   $162.80  
  Purchase #7 $199.87   5.517%   $210.8968   $210.90   $210.90   $210.90  
  7 purchase totals = $1,027.49       $1,095.7510   $1,095.75   $1,095.80   $1,095.70