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 $191.45   9.144%   $208.9562   $208.96   $208.95   $209.00  
  Purchase #2 $197.89   8.492%   $214.6948   $214.69   $214.70   $214.70  
  Purchase #3 $84.98   11.122%   $94.4315   $94.43   $94.45   $94.40  
  Purchase #4 $208.36   5.568%   $219.9615   $219.96   $219.95   $220.00  
  Purchase #5 $80.26   13.807%   $91.3415   $91.34   $91.35   $91.30  
  Purchase #6 $19.34   5.212%   $20.348   $20.35   $20.35   $20.30  
  Purchase #7 $196.40   3.697%   $203.6609   $203.66   $203.65   $203.70  
  7 purchase totals = $978.68       $1,053.3944   $1,053.39   $1,053.40   $1,053.40