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 $88.79   7.106%   $95.0994   $95.10   $95.10   $95.10  
  Purchase #2 $135.59   7.435%   $145.6711   $145.67   $145.65   $145.70  
  Purchase #3 $167.84   3.770%   $174.1676   $174.17   $174.15   $174.20  
  Purchase #4 $250.55   6.754%   $267.4721   $267.47   $267.45   $267.50  
  Purchase #5 $236.93   7.512%   $254.7282   $254.73   $254.75   $254.70  
  Purchase #6 $120.74   12.794%   $136.1875   $136.19   $136.20   $136.20  
  Purchase #7 $120.78   13.718%   $137.3486   $137.35   $137.35   $137.30  
  7 purchase totals = $1,121.22       $1,210.6745   $1,210.68   $1,210.65   $1,210.70