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 $44.46   6.701%   $47.4393   $47.44   $47.45   $47.40  
  Purchase #2 $220.58   7.387%   $236.8742   $236.87   $236.85   $236.90  
  Purchase #3 $203.33   4.775%   $213.039   $213.04   $213.05   $213.00  
  Purchase #4 $237.78   9.305%   $259.9054   $259.91   $259.90   $259.90  
  Purchase #5 $130.55   9.601%   $143.0841   $143.08   $143.10   $143.10  
  Purchase #6 $178.35   4.586%   $186.5291   $186.53   $186.55   $186.50  
  Purchase #7 $42.80   10.816%   $47.4292   $47.43   $47.45   $47.40  
  7 purchase totals = $1,057.85       $1,134.3003   $1,134.30   $1,134.35   $1,134.20