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 $85.65   13.294%   $97.0363   $97.04   $97.05   $97.00  
  Purchase #2 $76.56   4.109%   $79.7059   $79.71   $79.70   $79.70  
  Purchase #3 $76.61   9.506%   $83.8925   $83.89   $83.90   $83.90  
  Purchase #4 $246.32   4.823%   $258.2   $258.20   $258.20   $258.20  
  Purchase #5 $148.46   12.545%   $167.0843   $167.08   $167.10   $167.10  
  Purchase #6 $208.40   9.860%   $228.9482   $228.95   $228.95   $228.90  
  Purchase #7 $114.88   4.638%   $120.2081   $120.21   $120.20   $120.20  
  7 purchase totals = $956.88       $1,035.0753   $1,035.08   $1,035.10   $1,035.00