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 $195.77   5.209%   $205.9677   $205.97   $205.95   $206.00  
  Purchase #2 $31.96   3.340%   $33.0275   $33.03   $33.05   $33.00  
  Purchase #3 $202.95   5.258%   $213.6211   $213.62   $213.60   $213.60  
  Purchase #4 $135.97   12.334%   $152.7405   $152.74   $152.75   $152.70  
  Purchase #5 $187.96   10.415%   $207.536   $207.54   $207.55   $207.50  
  Purchase #6 $189.90   13.797%   $216.1005   $216.10   $216.10   $216.10  
  Purchase #7 $230.69   7.230%   $247.3689   $247.37   $247.35   $247.40  
  7 purchase totals = $1,175.20       $1,276.3622   $1,276.37   $1,276.35   $1,276.30