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 $95.51   12.113%   $107.0791   $107.08   $107.10   $107.10  
  Purchase #2 $164.71   7.555%   $177.1538   $177.15   $177.15   $177.20  
  Purchase #3 $244.82   6.120%   $259.803   $259.80   $259.80   $259.80  
  Purchase #4 $185.82   10.696%   $205.6953   $205.70   $205.70   $205.70  
  Purchase #5 $203.44   5.274%   $214.1694   $214.17   $214.15   $214.20  
  Purchase #6 $243.75   4.745%   $255.3159   $255.32   $255.30   $255.30  
  Purchase #7 $246.80   6.574%   $263.0246   $263.02   $263.00   $263.00  
  7 purchase totals = $1,384.85       $1,482.2411   $1,482.24   $1,482.20   $1,482.30