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 $214.84   3.868%   $223.15   $223.15   $223.15   $223.20  
  Purchase #2 $49.26   3.517%   $50.9925   $50.99   $51.00   $51.00  
  Purchase #3 $203.60   4.162%   $212.0738   $212.07   $212.05   $212.10  
  Purchase #4 $231.64   6.617%   $246.9676   $246.97   $246.95   $247.00  
  Purchase #5 $239.30   5.789%   $253.1531   $253.15   $253.15   $253.20  
  Purchase #6 $190.94   12.599%   $214.9965   $215.00   $215.00   $215.00  
  Purchase #7 $59.55   3.310%   $61.5211   $61.52   $61.50   $61.50  
  7 purchase totals = $1,189.13       $1,262.8546   $1,262.85   $1,262.80   $1,263.00