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 $196.79   11.602%   $219.6216   $219.62   $219.60   $219.60  
  Purchase #2 $106.95   5.309%   $112.628   $112.63   $112.65   $112.60  
  Purchase #3 $96.58   8.341%   $104.6357   $104.64   $104.65   $104.60  
  Purchase #4 $90.54   7.644%   $97.4609   $97.46   $97.45   $97.50  
  Purchase #5 $80.94   6.679%   $86.346   $86.35   $86.35   $86.30  
  Purchase #6 $247.85   12.433%   $278.6652   $278.67   $278.65   $278.70  
  Purchase #7 $238.70   6.513%   $254.2465   $254.25   $254.25   $254.20  
  7 purchase totals = $1,058.35       $1,153.6039   $1,153.62   $1,153.60   $1,153.50