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 $88.90   7.580%   $95.6386   $95.64   $95.65   $95.60  
  Purchase #2 $181.37   13.401%   $205.6754   $205.68   $205.70   $205.70  
  Purchase #3 $210.30   5.300%   $221.4459   $221.45   $221.45   $221.40  
  Purchase #4 $221.94   6.517%   $236.4038   $236.40   $236.40   $236.40  
  Purchase #5 $8.65   7.164%   $9.2697   $9.27   $9.25   $9.30  
  Purchase #6 $171.37   6.331%   $182.2194   $182.22   $182.20   $182.20  
  Purchase #7 $63.79   8.782%   $69.392   $69.39   $69.40   $69.40  
  7 purchase totals = $946.32       $1,020.0448   $1,020.05   $1,020.05   $1,020.00