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 $87.80   8.226%   $95.0224   $95.02   $95.00   $95.00  
  Purchase #2 $47.97   8.822%   $52.2019   $52.20   $52.20   $52.20  
  Purchase #3 $156.29   11.831%   $174.7807   $174.78   $174.80   $174.80  
  Purchase #4 $74.84   3.308%   $77.3157   $77.32   $77.30   $77.30  
  Purchase #5 $203.53   12.244%   $228.4502   $228.45   $228.45   $228.50  
  Purchase #6 $119.40   11.847%   $133.5453   $133.55   $133.55   $133.50  
  Purchase #7 $115.41   4.815%   $120.967   $120.97   $120.95   $121.00  
  7 purchase totals = $805.24       $882.2832   $882.29   $882.25   $882.30