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 $185.67   8.241%   $200.9711   $200.97   $200.95   $201.00  
  Purchase #2 $140.33   4.828%   $147.1051   $147.11   $147.10   $147.10  
  Purchase #3 $69.93   6.260%   $74.3076   $74.31   $74.30   $74.30  
  Purchase #4 $111.39   4.443%   $116.3391   $116.34   $116.35   $116.30  
  Purchase #5 $85.68   8.711%   $93.1436   $93.14   $93.15   $93.10  
  Purchase #6 $236.70   4.172%   $246.5751   $246.58   $246.60   $246.60  
  Purchase #7 $169.58   12.774%   $191.2421   $191.24   $191.25   $191.20  
  7 purchase totals = $999.28       $1,069.6837   $1,069.69   $1,069.70   $1,069.60