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 $62.61   3.862%   $65.028   $65.03   $65.05   $65.00  
  Purchase #2 $221.43   13.609%   $251.5644   $251.56   $251.55   $251.60  
  Purchase #3 $234.49   9.619%   $257.0456   $257.05   $257.05   $257.00  
  Purchase #4 $223.83   10.142%   $246.5308   $246.53   $246.55   $246.50  
  Purchase #5 $35.90   3.372%   $37.1105   $37.11   $37.10   $37.10  
  Purchase #6 $152.40   10.189%   $167.928   $167.93   $167.95   $167.90  
  Purchase #7 $135.49   4.540%   $141.6412   $141.64   $141.65   $141.60  
  7 purchase totals = $1,066.15       $1,166.8485   $1,166.85   $1,166.90   $1,166.70