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 $58.27   9.350%   $63.7182   $63.72   $63.70   $63.70  
  Purchase #2 $131.67   13.739%   $149.7601   $149.76   $149.75   $149.80  
  Purchase #3 $216.45   9.360%   $236.7097   $236.71   $236.70   $236.70  
  Purchase #4 $35.98   7.168%   $38.559   $38.56   $38.55   $38.60  
  Purchase #5 $225.66   5.670%   $238.4549   $238.45   $238.45   $238.50  
  Purchase #6 $94.28   4.572%   $98.5905   $98.59   $98.60   $98.60  
  Purchase #7 $165.80   13.570%   $188.2991   $188.30   $188.30   $188.30  
  7 purchase totals = $928.11       $1,014.0915   $1,014.09   $1,014.05   $1,014.20