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 $179.58   11.476%   $200.1886   $200.19   $200.20   $200.20  
  Purchase #2 $181.46   12.773%   $204.6379   $204.64   $204.65   $204.60  
  Purchase #3 $191.49   6.491%   $203.9196   $203.92   $203.90   $203.90  
  Purchase #4 $124.65   6.564%   $132.832   $132.83   $132.85   $132.80  
  Purchase #5 $107.76   6.236%   $114.4799   $114.48   $114.50   $114.50  
  Purchase #6 $119.93   11.256%   $133.4293   $133.43   $133.45   $133.40  
  Purchase #7 $97.91   7.201%   $104.9605   $104.96   $104.95   $105.00  
  7 purchase totals = $1,002.78       $1,094.4478   $1,094.45   $1,094.50   $1,094.40