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 $85.28   11.826%   $95.3652   $95.37   $95.35   $95.40  
  Purchase #2 $126.60   11.121%   $140.6792   $140.68   $140.70   $140.70  
  Purchase #3 $223.61   4.430%   $233.5159   $233.52   $233.50   $233.50  
  Purchase #4 $207.98   5.596%   $219.6186   $219.62   $219.60   $219.60  
  Purchase #5 $174.74   4.771%   $183.0768   $183.08   $183.10   $183.10  
  Purchase #6 $217.76   4.155%   $226.8079   $226.81   $226.80   $226.80  
  Purchase #7 $60.74   5.782%   $64.252   $64.25   $64.25   $64.30  
  7 purchase totals = $1,096.71       $1,163.3156   $1,163.33   $1,163.30   $1,163.40