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 $87.60   10.403%   $96.713   $96.71   $96.70   $96.70  
  Purchase #2 $144.32   9.148%   $157.5224   $157.52   $157.50   $157.50  
  Purchase #3 $123.28   5.328%   $129.8484   $129.85   $129.85   $129.80  
  Purchase #4 $103.92   5.215%   $109.3394   $109.34   $109.35   $109.30  
  Purchase #5 $100.31   9.352%   $109.691   $109.69   $109.70   $109.70  
  Purchase #6 $225.65   7.129%   $241.7366   $241.74   $241.75   $241.70  
  Purchase #7 $196.26   11.412%   $218.6572   $218.66   $218.65   $218.70  
  7 purchase totals = $981.34       $1,063.5080   $1,063.51   $1,063.50   $1,063.40