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 $190.91   5.424%   $201.265   $201.27   $201.25   $201.30  
  Purchase #2 $41.97   6.844%   $44.8424   $44.84   $44.85   $44.80  
  Purchase #3 $90.64   7.705%   $97.6238   $97.62   $97.60   $97.60  
  Purchase #4 $160.29   11.746%   $179.1177   $179.12   $179.10   $179.10  
  Purchase #5 $9.49   9.672%   $10.4079   $10.41   $10.40   $10.40  
  Purchase #6 $34.34   3.675%   $35.602   $35.60   $35.60   $35.60  
  Purchase #7 $171.40   12.290%   $192.4651   $192.47   $192.45   $192.50  
  7 purchase totals = $699.04       $761.3239   $761.33   $761.25   $761.30