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 $59.48   5.440%   $62.7157   $62.72   $62.70   $62.70  
  Purchase #2 $140.45   9.545%   $153.856   $153.86   $153.85   $153.90  
  Purchase #3 $210.67   6.535%   $224.4373   $224.44   $224.45   $224.40  
  Purchase #4 $152.71   10.568%   $168.8484   $168.85   $168.85   $168.80  
  Purchase #5 $98.31   8.814%   $106.975   $106.98   $107.00   $107.00  
  Purchase #6 $24.94   5.434%   $26.2952   $26.30   $26.30   $26.30  
  Purchase #7 $86.60   13.701%   $98.4651   $98.47   $98.45   $98.50  
  7 purchase totals = $773.16       $841.5927   $841.62   $841.60   $841.60