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 $119.51   5.653%   $126.2659   $126.27   $126.25   $126.30  
  Purchase #2 $200.33   8.238%   $216.8332   $216.83   $216.85   $216.80  
  Purchase #3 $243.97   13.862%   $277.7891   $277.79   $277.80   $277.80  
  Purchase #4 $66.85   4.504%   $69.8609   $69.86   $69.85   $69.90  
  Purchase #5 $169.32   11.294%   $188.443   $188.44   $188.45   $188.40  
  Purchase #6 $47.98   10.383%   $52.9618   $52.96   $52.95   $53.00  
  Purchase #7 $118.60   10.403%   $130.938   $130.94   $130.95   $130.90  
  7 purchase totals = $966.56       $1,063.0919   $1,063.09   $1,063.10   $1,063.10