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 $62.51   8.141%   $67.5989   $67.60   $67.60   $67.60  
  Purchase #2 $179.97   8.272%   $194.8571   $194.86   $194.85   $194.90  
  Purchase #3 $224.94   8.175%   $243.3288   $243.33   $243.35   $243.30  
  Purchase #4 $140.55   8.434%   $152.404   $152.40   $152.40   $152.40  
  Purchase #5 $145.37   11.518%   $162.1137   $162.11   $162.10   $162.10  
  Purchase #6 $54.85   4.816%   $57.4916   $57.49   $57.50   $57.50  
  Purchase #7 $248.44   3.493%   $257.118   $257.12   $257.10   $257.10  
  7 purchase totals = $1,056.63       $1,134.9121   $1,134.91   $1,134.90   $1,134.90