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 $75.55   8.568%   $82.0231   $82.02   $82.00   $82.00  
  Purchase #2 $156.92   12.664%   $176.7923   $176.79   $176.80   $176.80  
  Purchase #3 $247.93   5.231%   $260.8992   $260.90   $260.90   $260.90  
  Purchase #4 $104.33   10.275%   $115.0499   $115.05   $115.05   $115.00  
  Purchase #5 $189.78   5.831%   $200.8461   $200.85   $200.85   $200.80  
  Purchase #6 $222.70   4.767%   $233.3161   $233.32   $233.30   $233.30  
  Purchase #7 $85.84   10.261%   $94.648   $94.65   $94.65   $94.60  
  7 purchase totals = $1,083.05       $1,163.5747   $1,163.58   $1,163.55   $1,163.40