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 $94.79   4.721%   $99.265   $99.27   $99.25   $99.30  
  Purchase #2 $22.62   6.466%   $24.0826   $24.08   $24.10   $24.10  
  Purchase #3 $183.92   4.777%   $192.7059   $192.71   $192.70   $192.70  
  Purchase #4 $212.91   6.784%   $227.3538   $227.35   $227.35   $227.40  
  Purchase #5 $95.60   11.135%   $106.2451   $106.25   $106.25   $106.20  
  Purchase #6 $46.85   8.133%   $50.6603   $50.66   $50.65   $50.70  
  Purchase #7 $31.32   7.450%   $33.6533   $33.65   $33.65   $33.70  
  7 purchase totals = $688.01       $733.9660   $733.97   $733.95   $734.10