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 $184.52   5.434%   $194.5468   $194.55   $194.55   $194.50  
  Purchase #2 $83.47   3.479%   $86.3739   $86.37   $86.35   $86.40  
  Purchase #3 $223.66   8.304%   $242.2327   $242.23   $242.25   $242.20  
  Purchase #4 $223.87   3.659%   $232.0614   $232.06   $232.05   $232.10  
  Purchase #5 $57.83   4.388%   $60.3676   $60.37   $60.35   $60.40  
  Purchase #6 $126.31   5.539%   $133.3063   $133.31   $133.30   $133.30  
  Purchase #7 $118.85   5.857%   $125.811   $125.81   $125.80   $125.80  
  7 purchase totals = $1,018.51       $1,074.6997   $1,074.70   $1,074.65   $1,074.70