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 $61.57   11.340%   $68.552   $68.55   $68.55   $68.60  
  Purchase #2 $196.58   11.864%   $219.9023   $219.90   $219.90   $219.90  
  Purchase #3 $80.58   8.280%   $87.252   $87.25   $87.25   $87.30  
  Purchase #4 $179.26   12.292%   $201.2946   $201.29   $201.30   $201.30  
  Purchase #5 $6.57   7.109%   $7.0371   $7.04   $7.05   $7.00  
  Purchase #6 $206.67   8.562%   $224.3651   $224.37   $224.35   $224.40  
  Purchase #7 $170.31   13.295%   $192.9527   $192.95   $192.95   $193.00  
  7 purchase totals = $901.54       $1,001.3558   $1,001.35   $1,001.35   $1,001.50