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 $168.61   8.122%   $182.3045   $182.30   $182.30   $182.30  
  Purchase #2 $14.43   13.551%   $16.3854   $16.39   $16.40   $16.40  
  Purchase #3 $33.28   10.565%   $36.796   $36.80   $36.80   $36.80  
  Purchase #4 $145.80   7.590%   $156.8662   $156.87   $156.85   $156.90  
  Purchase #5 $161.55   6.117%   $171.432   $171.43   $171.45   $171.40  
  Purchase #6 $155.28   10.290%   $171.2583   $171.26   $171.25   $171.30  
  Purchase #7 $23.85   7.405%   $25.6161   $25.62   $25.60   $25.60  
  7 purchase totals = $702.80       $760.6585   $760.67   $760.65   $760.70