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 $184.48   5.151%   $193.9826   $193.98   $194.00   $194.00  
  Purchase #2 $87.72   8.123%   $94.8455   $94.85   $94.85   $94.80  
  Purchase #3 $206.27   3.800%   $214.1083   $214.11   $214.10   $214.10  
  Purchase #4 $250.45   10.820%   $277.5487   $277.55   $277.55   $277.50  
  Purchase #5 $138.89   9.107%   $151.5387   $151.54   $151.55   $151.50  
  Purchase #6 $87.90   6.252%   $93.3955   $93.40   $93.40   $93.40  
  Purchase #7 $83.81   12.402%   $94.2041   $94.20   $94.20   $94.20  
  7 purchase totals = $1,039.52       $1,119.6234   $1,119.63   $1,119.65   $1,119.50