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 $88.29   7.203%   $94.6495   $94.65   $94.65   $94.60  
  Purchase #2 $90.68   3.313%   $93.6842   $93.68   $93.70   $93.70  
  Purchase #3 $37.92   13.509%   $43.0426   $43.04   $43.05   $43.00  
  Purchase #4 $190.36   7.208%   $204.0811   $204.08   $204.10   $204.10  
  Purchase #5 $114.88   8.561%   $124.7149   $124.71   $124.70   $124.70  
  Purchase #6 $235.75   10.512%   $260.532   $260.53   $260.55   $260.50  
  Purchase #7 $196.57   11.856%   $219.8753   $219.88   $219.90   $219.90  
  7 purchase totals = $954.45       $1,040.5796   $1,040.57   $1,040.65   $1,040.50