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 $212.63   3.314%   $219.6766   $219.68   $219.70   $219.70  
  Purchase #2 $198.57   7.675%   $213.8102   $213.81   $213.80   $213.80  
  Purchase #3 $39.73   3.691%   $41.1964   $41.20   $41.20   $41.20  
  Purchase #4 $71.32   6.619%   $76.0407   $76.04   $76.05   $76.00  
  Purchase #5 $215.70   5.857%   $228.3335   $228.33   $228.35   $228.30  
  Purchase #6 $173.72   9.642%   $190.4701   $190.47   $190.45   $190.50  
  Purchase #7 $39.86   12.233%   $44.7361   $44.74   $44.75   $44.70  
  7 purchase totals = $951.53       $1,014.2636   $1,014.27   $1,014.30   $1,014.20