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 $44.27   6.572%   $47.1794   $47.18   $47.20   $47.20  
  Purchase #2 $111.82   12.845%   $126.1833   $126.18   $126.20   $126.20  
  Purchase #3 $157.85   9.827%   $173.3619   $173.36   $173.35   $173.40  
  Purchase #4 $175.37   4.523%   $183.302   $183.30   $183.30   $183.30  
  Purchase #5 $176.74   3.719%   $183.313   $183.31   $183.30   $183.30  
  Purchase #6 $177.61   13.430%   $201.463   $201.46   $201.45   $201.50  
  Purchase #7 $182.59   12.158%   $204.7893   $204.79   $204.80   $204.80  
  7 purchase totals = $1,026.25       $1,119.5919   $1,119.58   $1,119.60   $1,119.70