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 $215.50   8.839%   $234.548   $234.55   $234.55   $234.50  
  Purchase #2 $123.42   3.349%   $127.5533   $127.55   $127.55   $127.60  
  Purchase #3 $49.41   12.168%   $55.4222   $55.42   $55.40   $55.40  
  Purchase #4 $223.35   6.252%   $237.3138   $237.31   $237.30   $237.30  
  Purchase #5 $244.74   3.744%   $253.9031   $253.90   $253.90   $253.90  
  Purchase #6 $135.73   9.124%   $148.114   $148.11   $148.10   $148.10  
  Purchase #7 $120.42   3.777%   $124.9683   $124.97   $124.95   $125.00  
  7 purchase totals = $1,112.57       $1,181.8227   $1,181.81   $1,181.75   $1,181.80