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 $41.63   7.334%   $44.6831   $44.68   $44.70   $44.70  
  Purchase #2 $200.91   9.141%   $219.2752   $219.28   $219.30   $219.30  
  Purchase #3 $180.37   11.816%   $201.6825   $201.68   $201.70   $201.70  
  Purchase #4 $238.25   4.755%   $249.5788   $249.58   $249.60   $249.60  
  Purchase #5 $80.29   3.115%   $82.791   $82.79   $82.80   $82.80  
  Purchase #6 $187.29   6.457%   $199.3833   $199.38   $199.40   $199.40  
  Purchase #7 $218.61   7.116%   $234.1663   $234.17   $234.15   $234.20  
  7 purchase totals = $1,147.35       $1,231.5602   $1,231.56   $1,231.65   $1,231.70