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 $96.49   9.814%   $105.9595   $105.96   $105.95   $106.00  
  Purchase #2 $165.61   3.563%   $171.5107   $171.51   $171.50   $171.50  
  Purchase #3 $182.69   11.145%   $203.0508   $203.05   $203.05   $203.10  
  Purchase #4 $94.47   12.821%   $106.582   $106.58   $106.60   $106.60  
  Purchase #5 $223.87   5.249%   $235.6209   $235.62   $235.60   $235.60  
  Purchase #6 $102.68   3.759%   $106.5397   $106.54   $106.55   $106.50  
  Purchase #7 $78.78   12.170%   $88.3675   $88.37   $88.35   $88.40  
  7 purchase totals = $944.59       $1,017.6311   $1,017.63   $1,017.60   $1,017.70