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 $116.48   8.653%   $126.559   $126.56   $126.55   $126.60  
  Purchase #2 $236.71   7.246%   $253.862   $253.86   $253.85   $253.90  
  Purchase #3 $47.83   9.392%   $52.3222   $52.32   $52.30   $52.30  
  Purchase #4 $237.96   4.118%   $247.7592   $247.76   $247.75   $247.80  
  Purchase #5 $219.31   6.520%   $233.609   $233.61   $233.60   $233.60  
  Purchase #6 $173.66   3.688%   $180.0646   $180.06   $180.05   $180.10  
  Purchase #7 $92.44   7.541%   $99.4109   $99.41   $99.40   $99.40  
  7 purchase totals = $1,124.39       $1,193.5869   $1,193.58   $1,193.50   $1,193.70