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 $69.65   7.195%   $74.6613   $74.66   $74.65   $74.70  
  Purchase #2 $116.29   10.315%   $128.2853   $128.29   $128.30   $128.30  
  Purchase #3 $67.50   8.173%   $73.0168   $73.02   $73.00   $73.00  
  Purchase #4 $103.68   11.654%   $115.7629   $115.76   $115.75   $115.80  
  Purchase #5 $245.42   8.626%   $266.5899   $266.59   $266.60   $266.60  
  Purchase #6 $209.49   5.583%   $221.1858   $221.19   $221.20   $221.20  
  Purchase #7 $140.71   4.633%   $147.2291   $147.23   $147.25   $147.20  
  7 purchase totals = $952.74       $1,026.7311   $1,026.74   $1,026.75   $1,026.80