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 $84.89   12.680%   $95.6541   $95.65   $95.65   $95.70  
  Purchase #2 $119.61   9.735%   $131.254   $131.25   $131.25   $131.30  
  Purchase #3 $167.25   13.215%   $189.3521   $189.35   $189.35   $189.40  
  Purchase #4 $134.38   13.592%   $152.6449   $152.64   $152.65   $152.60  
  Purchase #5 $87.35   13.169%   $98.8531   $98.85   $98.85   $98.90  
  Purchase #6 $15.33   7.805%   $16.5265   $16.53   $16.55   $16.50  
  Purchase #7 $187.38   12.226%   $210.2891   $210.29   $210.30   $210.30  
  7 purchase totals = $796.19       $894.5738   $894.56   $894.60   $894.70