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 $191.51   5.826%   $202.6674   $202.67   $202.65   $202.70  
  Purchase #2 $97.67   6.586%   $104.1025   $104.10   $104.10   $104.10  
  Purchase #3 $59.66   11.789%   $66.6933   $66.69   $66.70   $66.70  
  Purchase #4 $130.89   10.435%   $144.5484   $144.55   $144.55   $144.50  
  Purchase #5 $236.68   4.285%   $246.8217   $246.82   $246.80   $246.80  
  Purchase #6 $121.32   10.684%   $134.2818   $134.28   $134.30   $134.30  
  Purchase #7 $209.94   6.372%   $223.3174   $223.32   $223.30   $223.30  
  7 purchase totals = $1,047.67       $1,122.4325   $1,122.43   $1,122.40   $1,122.40