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 $173.63   12.610%   $195.5247   $195.52   $195.50   $195.50  
  Purchase #2 $206.45   9.869%   $226.8246   $226.82   $226.80   $226.80  
  Purchase #3 $134.74   9.426%   $147.4406   $147.44   $147.45   $147.40  
  Purchase #4 $242.26   3.138%   $249.8621   $249.86   $249.85   $249.90  
  Purchase #5 $151.52   11.277%   $168.6069   $168.61   $168.60   $168.60  
  Purchase #6 $140.60   4.112%   $146.3815   $146.38   $146.40   $146.40  
  Purchase #7 $52.95   12.489%   $59.5629   $59.56   $59.55   $59.60  
  7 purchase totals = $1,102.15       $1,194.2033   $1,194.19   $1,194.15   $1,194.20