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 $91.39   5.723%   $96.6202   $96.62   $96.60   $96.60  
  Purchase #2 $250.33   4.164%   $260.7537   $260.75   $260.75   $260.80  
  Purchase #3 $15.71   4.787%   $16.462   $16.46   $16.45   $16.50  
  Purchase #4 $193.97   11.616%   $216.5016   $216.50   $216.50   $216.50  
  Purchase #5 $212.64   8.123%   $229.9127   $229.91   $229.90   $229.90  
  Purchase #6 $166.86   11.841%   $186.6179   $186.62   $186.60   $186.60  
  Purchase #7 $65.82   3.459%   $68.0967   $68.10   $68.10   $68.10  
  7 purchase totals = $996.72       $1,074.9648   $1,074.96   $1,074.90   $1,075.00