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 $69.46   11.361%   $77.3514   $77.35   $77.35   $77.40  
  Purchase #2 $222.92   4.687%   $233.3683   $233.37   $233.35   $233.40  
  Purchase #3 $45.29   8.369%   $49.0803   $49.08   $49.10   $49.10  
  Purchase #4 $93.48   9.580%   $102.4354   $102.44   $102.45   $102.40  
  Purchase #5 $11.46   13.110%   $12.9624   $12.96   $12.95   $13.00  
  Purchase #6 $115.76   7.299%   $124.2093   $124.21   $124.20   $124.20  
  Purchase #7 $175.44   11.594%   $195.7805   $195.78   $195.80   $195.80  
  7 purchase totals = $733.81       $795.1876   $795.19   $795.20   $795.30