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 $233.74   12.547%   $263.0674   $263.07   $263.05   $263.10  
  Purchase #2 $159.97   5.525%   $168.8083   $168.81   $168.80   $168.80  
  Purchase #3 $24.55   6.718%   $26.1993   $26.20   $26.20   $26.20  
  Purchase #4 $186.79   4.829%   $195.8101   $195.81   $195.80   $195.80  
  Purchase #5 $187.73   6.671%   $200.2535   $200.25   $200.25   $200.30  
  Purchase #6 $219.84   11.497%   $245.115   $245.12   $245.10   $245.10  
  Purchase #7 $64.96   4.278%   $67.739   $67.74   $67.75   $67.70  
  7 purchase totals = $1,077.58       $1,166.9926   $1,167.00   $1,166.95   $1,167.00