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 $176.25   9.784%   $193.4943   $193.49   $193.50   $193.50  
  Purchase #2 $216.69   8.301%   $234.6774   $234.68   $234.70   $234.70  
  Purchase #3 $193.91   6.505%   $206.5238   $206.52   $206.50   $206.50  
  Purchase #4 $55.80   13.462%   $63.3118   $63.31   $63.30   $63.30  
  Purchase #5 $75.93   9.115%   $82.851   $82.85   $82.85   $82.90  
  Purchase #6 $120.54   3.775%   $125.0904   $125.09   $125.10   $125.10  
  Purchase #7 $101.37   5.457%   $106.9018   $106.90   $106.90   $106.90  
  7 purchase totals = $940.49       $1,012.8505   $1,012.84   $1,012.85   $1,012.90