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 $184.95   9.450%   $202.4278   $202.43   $202.45   $202.40  
  Purchase #2 $151.47   9.387%   $165.6885   $165.69   $165.70   $165.70  
  Purchase #3 $47.32   11.184%   $52.6123   $52.61   $52.60   $52.60  
  Purchase #4 $152.83   10.717%   $169.2088   $169.21   $169.20   $169.20  
  Purchase #5 $183.42   4.273%   $191.2575   $191.26   $191.25   $191.30  
  Purchase #6 $186.94   13.711%   $212.5713   $212.57   $212.55   $212.60  
  Purchase #7 $65.49   8.438%   $71.016   $71.02   $71.00   $71.00  
  7 purchase totals = $972.42       $1,064.7822   $1,064.79   $1,064.75   $1,064.80