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 $41.82   6.787%   $44.6583   $44.66   $44.65   $44.70  
  Purchase #2 $163.79   3.597%   $169.6815   $169.68   $169.70   $169.70  
  Purchase #3 $82.76   13.729%   $94.1221   $94.12   $94.10   $94.10  
  Purchase #4 $79.29   5.751%   $83.85   $83.85   $83.85   $83.90  
  Purchase #5 $234.55   3.470%   $242.6889   $242.69   $242.70   $242.70  
  Purchase #6 $36.42   4.649%   $38.1132   $38.11   $38.10   $38.10  
  Purchase #7 $228.31   5.690%   $241.3008   $241.30   $241.30   $241.30  
  7 purchase totals = $866.94       $914.4148   $914.41   $914.40   $914.50