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 $97.69   10.199%   $107.6534   $107.65   $107.65   $107.70  
  Purchase #2 $230.79   11.747%   $257.9009   $257.90   $257.90   $257.90  
  Purchase #3 $228.65   10.163%   $251.8877   $251.89   $251.90   $251.90  
  Purchase #4 $156.37   10.356%   $172.5637   $172.56   $172.55   $172.60  
  Purchase #5 $236.70   7.141%   $253.6027   $253.60   $253.60   $253.60  
  Purchase #6 $177.96   9.502%   $194.8698   $194.87   $194.85   $194.90  
  Purchase #7 $202.94   9.115%   $221.438   $221.44   $221.45   $221.40  
  7 purchase totals = $1,331.10       $1,459.9162   $1,459.91   $1,459.90   $1,460.00