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 $191.35   8.525%   $207.6626   $207.66   $207.65   $207.70  
  Purchase #2 $147.58   10.519%   $163.1039   $163.10   $163.10   $163.10  
  Purchase #3 $70.96   5.654%   $74.9721   $74.97   $74.95   $75.00  
  Purchase #4 $230.27   4.665%   $241.0121   $241.01   $241.00   $241.00  
  Purchase #5 $51.70   5.563%   $54.5761   $54.58   $54.60   $54.60  
  Purchase #6 $181.25   5.685%   $191.5541   $191.55   $191.55   $191.60  
  Purchase #7 $236.80   6.339%   $251.8108   $251.81   $251.80   $251.80  
  7 purchase totals = $1,109.91       $1,184.6917   $1,184.68   $1,184.65   $1,184.80