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 $230.35   13.844%   $262.2397   $262.24   $262.25   $262.20  
  Purchase #2 $206.52   4.205%   $215.2042   $215.20   $215.20   $215.20  
  Purchase #3 $185.34   8.384%   $200.8789   $200.88   $200.90   $200.90  
  Purchase #4 $215.85   4.323%   $225.1812   $225.18   $225.20   $225.20  
  Purchase #5 $60.73   4.787%   $63.6371   $63.64   $63.65   $63.60  
  Purchase #6 $22.74   6.437%   $24.2038   $24.20   $24.20   $24.20  
  Purchase #7 $192.54   13.115%   $217.7916   $217.79   $217.80   $217.80  
  7 purchase totals = $1,114.07       $1,209.1365   $1,209.13   $1,209.20   $1,209.10