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 $191.44   7.426%   $205.6563   $205.66   $205.65   $205.70  
  Purchase #2 $188.79   9.634%   $206.978   $206.98   $207.00   $207.00  
  Purchase #3 $24.70   5.567%   $26.075   $26.08   $26.10   $26.10  
  Purchase #4 $109.65   11.466%   $122.2225   $122.22   $122.20   $122.20  
  Purchase #5 $176.41   9.279%   $192.7791   $192.78   $192.80   $192.80  
  Purchase #6 $167.55   5.874%   $177.3919   $177.39   $177.40   $177.40  
  Purchase #7 $105.47   4.748%   $110.4777   $110.48   $110.50   $110.50  
  7 purchase totals = $964.01       $1,041.5805   $1,041.59   $1,041.65   $1,041.70