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 $56.36   4.377%   $58.8269   $58.83   $58.85   $58.80  
  Purchase #2 $179.42   4.425%   $187.3593   $187.36   $187.35   $187.40  
  Purchase #3 $241.57   3.606%   $250.281   $250.28   $250.30   $250.30  
  Purchase #4 $177.64   9.208%   $193.9971   $194.00   $194.00   $194.00  
  Purchase #5 $116.97   9.148%   $127.6704   $127.67   $127.65   $127.70  
  Purchase #6 $98.42   4.611%   $102.9581   $102.96   $102.95   $103.00  
  Purchase #7 $79.78   13.499%   $90.5495   $90.55   $90.55   $90.50  
  7 purchase totals = $950.16       $1,011.6423   $1,011.65   $1,011.65   $1,011.70