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 $153.87   10.125%   $169.4493   $169.45   $169.45   $169.40  
  Purchase #2 $178.88   13.387%   $202.8267   $202.83   $202.85   $202.80  
  Purchase #3 $11.79   7.476%   $12.6714   $12.67   $12.65   $12.70  
  Purchase #4 $201.90   7.677%   $217.3999   $217.40   $217.40   $217.40  
  Purchase #5 $170.97   6.231%   $181.6231   $181.62   $181.60   $181.60  
  Purchase #6 $214.83   9.481%   $235.198   $235.20   $235.20   $235.20  
  Purchase #7 $112.39   3.205%   $115.9921   $115.99   $116.00   $116.00  
  7 purchase totals = $1,044.63       $1,135.1605   $1,135.16   $1,135.15   $1,135.10