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 $115.41   9.743%   $126.6544   $126.65   $126.65   $126.70  
  Purchase #2 $86.43   13.323%   $97.9451   $97.95   $97.95   $97.90  
  Purchase #3 $211.60   9.689%   $232.1019   $232.10   $232.10   $232.10  
  Purchase #4 $170.75   9.383%   $186.7715   $186.77   $186.75   $186.80  
  Purchase #5 $191.32   6.581%   $203.9108   $203.91   $203.90   $203.90  
  Purchase #6 $144.73   6.640%   $154.3401   $154.34   $154.35   $154.30  
  Purchase #7 $186.81   4.110%   $194.4879   $194.49   $194.50   $194.50  
  7 purchase totals = $1,107.05       $1,196.2117   $1,196.21   $1,196.20   $1,196.20