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 $63.38   3.823%   $65.803   $65.80   $65.80   $65.80  
  Purchase #2 $200.54   9.831%   $220.2551   $220.26   $220.25   $220.30  
  Purchase #3 $153.37   11.855%   $171.552   $171.55   $171.55   $171.60  
  Purchase #4 $44.94   4.716%   $47.0594   $47.06   $47.05   $47.10  
  Purchase #5 $235.46   8.267%   $254.9255   $254.93   $254.95   $254.90  
  Purchase #6 $161.61   7.558%   $173.8245   $173.82   $173.80   $173.80  
  Purchase #7 $206.93   5.841%   $219.0168   $219.02   $219.00   $219.00  
  7 purchase totals = $1,066.23       $1,152.4363   $1,152.44   $1,152.40   $1,152.50