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 $41.71   13.619%   $47.3905   $47.39   $47.40   $47.40  
  Purchase #2 $220.57   5.557%   $232.8271   $232.83   $232.85   $232.80  
  Purchase #3 $68.49   7.589%   $73.6877   $73.69   $73.70   $73.70  
  Purchase #4 $192.58   9.868%   $211.5838   $211.58   $211.60   $211.60  
  Purchase #5 $159.78   10.166%   $176.0232   $176.02   $176.00   $176.00  
  Purchase #6 $205.43   13.485%   $233.1322   $233.13   $233.15   $233.10  
  Purchase #7 $218.33   4.828%   $228.871   $228.87   $228.85   $228.90  
  7 purchase totals = $1,106.89       $1,203.5155   $1,203.51   $1,203.55   $1,203.50