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 $118.87   4.683%   $124.4367   $124.44   $124.45   $124.40  
  Purchase #2 $217.81   6.562%   $232.1027   $232.10   $232.10   $232.10  
  Purchase #3 $34.87   3.149%   $35.9681   $35.97   $35.95   $36.00  
  Purchase #4 $239.49   12.573%   $269.6011   $269.60   $269.60   $269.60  
  Purchase #5 $60.96   12.396%   $68.5166   $68.52   $68.50   $68.50  
  Purchase #6 $159.74   8.731%   $173.6869   $173.69   $173.70   $173.70  
  Purchase #7 $182.98   3.680%   $189.7137   $189.71   $189.70   $189.70  
  7 purchase totals = $1,014.72       $1,094.0258   $1,094.03   $1,094.00   $1,094.00