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 $59.70   4.421%   $62.3393   $62.34   $62.35   $62.30  
  Purchase #2 $243.93   10.307%   $269.0719   $269.07   $269.05   $269.10  
  Purchase #3 $53.62   12.127%   $60.1225   $60.12   $60.10   $60.10  
  Purchase #4 $214.73   5.198%   $225.8917   $225.89   $225.90   $225.90  
  Purchase #5 $139.79   5.487%   $147.4603   $147.46   $147.45   $147.50  
  Purchase #6 $218.81   9.109%   $238.7414   $238.74   $238.75   $238.70  
  Purchase #7 $222.47   8.141%   $240.5813   $240.58   $240.60   $240.60  
  7 purchase totals = $1,153.05       $1,244.2084   $1,244.20   $1,244.20   $1,244.20