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 $198.48   6.743%   $211.8635   $211.86   $211.85   $211.90  
  Purchase #2 $222.93   4.359%   $232.6475   $232.65   $232.65   $232.60  
  Purchase #3 $98.69   8.324%   $106.905   $106.91   $106.90   $106.90  
  Purchase #4 $103.39   9.815%   $113.5377   $113.54   $113.55   $113.50  
  Purchase #5 $150.64   6.474%   $160.3924   $160.39   $160.40   $160.40  
  Purchase #6 $149.53   4.590%   $156.3934   $156.39   $156.40   $156.40  
  Purchase #7 $58.60   4.607%   $61.2997   $61.30   $61.30   $61.30  
  7 purchase totals = $982.26       $1,043.0392   $1,043.04   $1,043.05   $1,043.00