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 $87.67   8.372%   $95.0097   $95.01   $95.00   $95.00  
  Purchase #2 $37.54   13.855%   $42.7412   $42.74   $42.75   $42.70  
  Purchase #3 $44.84   3.156%   $46.2552   $46.26   $46.25   $46.30  
  Purchase #4 $225.98   8.349%   $244.8471   $244.85   $244.85   $244.80  
  Purchase #5 $7.41   6.106%   $7.8625   $7.86   $7.85   $7.90  
  Purchase #6 $89.75   5.255%   $94.4664   $94.47   $94.45   $94.50  
  Purchase #7 $179.40   12.748%   $202.2699   $202.27   $202.25   $202.30  
  7 purchase totals = $672.59       $733.4520   $733.46   $733.40   $733.50