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 $33.58   4.337%   $35.0364   $35.04   $35.05   $35.00  
  Purchase #2 $214.85   9.723%   $235.7399   $235.74   $235.75   $235.70  
  Purchase #3 $166.80   4.512%   $174.326   $174.33   $174.35   $174.30  
  Purchase #4 $88.98   9.176%   $97.1448   $97.14   $97.15   $97.10  
  Purchase #5 $121.26   3.843%   $125.92   $125.92   $125.90   $125.90  
  Purchase #6 $159.40   6.845%   $170.3109   $170.31   $170.30   $170.30  
  Purchase #7 $198.74   11.281%   $221.1599   $221.16   $221.15   $221.20  
  7 purchase totals = $983.61       $1,059.6379   $1,059.64   $1,059.65   $1,059.50