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 $226.95   5.579%   $239.6115   $239.61   $239.60   $239.60  
  Purchase #2 $57.28   5.717%   $60.5547   $60.55   $60.55   $60.60  
  Purchase #3 $201.39   10.874%   $223.2891   $223.29   $223.30   $223.30  
  Purchase #4 $163.37   8.107%   $176.6144   $176.61   $176.60   $176.60  
  Purchase #5 $29.47   11.860%   $32.9651   $32.97   $32.95   $33.00  
  Purchase #6 $89.92   9.568%   $98.5235   $98.52   $98.50   $98.50  
  Purchase #7 $190.51   5.263%   $200.5365   $200.54   $200.55   $200.50  
  7 purchase totals = $958.89       $1,032.0948   $1,032.09   $1,032.05   $1,032.10