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 $195.40   3.180%   $201.6137   $201.61   $201.60   $201.60  
  Purchase #2 $124.79   12.419%   $140.2877   $140.29   $140.30   $140.30  
  Purchase #3 $218.77   7.456%   $235.0815   $235.08   $235.10   $235.10  
  Purchase #4 $76.59   7.169%   $82.0807   $82.08   $82.10   $82.10  
  Purchase #5 $116.95   6.498%   $124.5494   $124.55   $124.55   $124.50  
  Purchase #6 $98.83   10.282%   $108.9917   $108.99   $109.00   $109.00  
  Purchase #7 $195.47   7.410%   $209.9543   $209.95   $209.95   $210.00  
  7 purchase totals = $1,026.80       $1,102.5590   $1,102.55   $1,102.60   $1,102.60