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 $184.38   4.451%   $192.5868   $192.59   $192.60   $192.60  
  Purchase #2 $112.96   8.329%   $122.3684   $122.37   $122.35   $122.40  
  Purchase #3 $56.87   7.140%   $60.9305   $60.93   $60.95   $60.90  
  Purchase #4 $45.95   3.791%   $47.692   $47.69   $47.70   $47.70  
  Purchase #5 $181.45   4.135%   $188.953   $188.95   $188.95   $189.00  
  Purchase #6 $215.48   3.828%   $223.7286   $223.73   $223.75   $223.70  
  Purchase #7 $114.53   3.332%   $118.3461   $118.35   $118.35   $118.30  
  7 purchase totals = $911.62       $954.6054   $954.61   $954.65   $954.60