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 $56.71   10.614%   $62.7292   $62.73   $62.75   $62.70  
  Purchase #2 $132.89   11.177%   $147.7431   $147.74   $147.75   $147.70  
  Purchase #3 $158.30   9.874%   $173.9305   $173.93   $173.95   $173.90  
  Purchase #4 $222.60   8.272%   $241.0135   $241.01   $241.00   $241.00  
  Purchase #5 $223.47   9.864%   $245.5131   $245.51   $245.50   $245.50  
  Purchase #6 $27.72   7.107%   $29.6901   $29.69   $29.70   $29.70  
  Purchase #7 $148.68   9.759%   $163.1897   $163.19   $163.20   $163.20  
  7 purchase totals = $970.37       $1,063.8092   $1,063.80   $1,063.85   $1,063.70