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 $216.28   4.844%   $226.7566   $226.76   $226.75   $226.80  
  Purchase #2 $220.96   5.276%   $232.6178   $232.62   $232.60   $232.60  
  Purchase #3 $239.88   9.516%   $262.707   $262.71   $262.70   $262.70  
  Purchase #4 $44.58   7.139%   $47.7626   $47.76   $47.75   $47.80  
  Purchase #5 $6.49   7.607%   $6.9837   $6.98   $7.00   $7.00  
  Purchase #6 $214.97   9.740%   $235.9081   $235.91   $235.90   $235.90  
  Purchase #7 $98.35   4.483%   $102.759   $102.76   $102.75   $102.80  
  7 purchase totals = $1,041.51       $1,115.4948   $1,115.50   $1,115.45   $1,115.60