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 $82.82   5.147%   $87.0827   $87.08   $87.10   $87.10  
  Purchase #2 $98.30   13.524%   $111.5941   $111.59   $111.60   $111.60  
  Purchase #3 $212.67   3.788%   $220.7259   $220.73   $220.75   $220.70  
  Purchase #4 $234.94   4.702%   $245.9869   $245.99   $246.00   $246.00  
  Purchase #5 $217.49   9.233%   $237.5709   $237.57   $237.55   $237.60  
  Purchase #6 $16.33   3.862%   $16.9607   $16.96   $16.95   $17.00  
  Purchase #7 $146.94   6.142%   $155.9651   $155.97   $155.95   $156.00  
  7 purchase totals = $1,009.49       $1,075.8863   $1,075.89   $1,075.90   $1,076.00