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 $141.69   7.737%   $152.6526   $152.65   $152.65   $152.70  
  Purchase #2 $170.71   13.612%   $193.947   $193.95   $193.95   $193.90  
  Purchase #3 $210.31   6.347%   $223.6584   $223.66   $223.65   $223.70  
  Purchase #4 $175.70   5.605%   $185.548   $185.55   $185.55   $185.50  
  Purchase #5 $195.27   3.296%   $201.7061   $201.71   $201.70   $201.70  
  Purchase #6 $156.52   9.665%   $171.6477   $171.65   $171.65   $171.60  
  Purchase #7 $191.97   10.485%   $212.0981   $212.10   $212.10   $212.10  
  7 purchase totals = $1,242.17       $1,341.2579   $1,341.27   $1,341.25   $1,341.20