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 $32.47   8.227%   $35.1413   $35.14   $35.15   $35.10  
  Purchase #2 $97.51   6.309%   $103.6619   $103.66   $103.65   $103.70  
  Purchase #3 $84.26   3.396%   $87.1215   $87.12   $87.10   $87.10  
  Purchase #4 $179.29   13.817%   $204.0625   $204.06   $204.05   $204.10  
  Purchase #5 $211.65   4.293%   $220.7361   $220.74   $220.75   $220.70  
  Purchase #6 $192.29   13.129%   $217.5358   $217.54   $217.55   $217.50  
  Purchase #7 $183.96   4.263%   $191.8022   $191.80   $191.80   $191.80  
  7 purchase totals = $981.43       $1,060.0613   $1,060.06   $1,060.05   $1,060.00