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 $61.60   11.788%   $68.8614   $68.86   $68.85   $68.90  
  Purchase #2 $133.37   9.341%   $145.8281   $145.83   $145.85   $145.80  
  Purchase #3 $96.44   4.241%   $100.53   $100.53   $100.55   $100.50  
  Purchase #4 $120.26   9.752%   $131.9878   $131.99   $132.00   $132.00  
  Purchase #5 $200.42   9.724%   $219.9088   $219.91   $219.90   $219.90  
  Purchase #6 $188.70   12.265%   $211.8441   $211.84   $211.85   $211.80  
  Purchase #7 $166.39   13.431%   $188.7378   $188.74   $188.75   $188.70  
  7 purchase totals = $967.18       $1,067.6980   $1,067.70   $1,067.75   $1,067.60