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 $162.85   11.731%   $181.9539   $181.95   $181.95   $182.00  
  Purchase #2 $166.31   12.343%   $186.8376   $186.84   $186.85   $186.80  
  Purchase #3 $51.73   6.798%   $55.2466   $55.25   $55.25   $55.20  
  Purchase #4 $204.73   3.822%   $212.5548   $212.55   $212.55   $212.60  
  Purchase #5 $112.87   3.713%   $117.0609   $117.06   $117.05   $117.10  
  Purchase #6 $130.63   12.668%   $147.1782   $147.18   $147.20   $147.20  
  Purchase #7 $156.70   13.306%   $177.5505   $177.55   $177.55   $177.60  
  7 purchase totals = $985.82       $1,078.3825   $1,078.38   $1,078.40   $1,078.50