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 $176.80   7.474%   $190.014   $190.01   $190.00   $190.00  
  Purchase #2 $44.65   9.626%   $48.948   $48.95   $48.95   $48.90  
  Purchase #3 $236.95   6.809%   $253.0839   $253.08   $253.10   $253.10  
  Purchase #4 $171.71   9.385%   $187.825   $187.83   $187.85   $187.80  
  Purchase #5 $94.29   3.238%   $97.3431   $97.34   $97.35   $97.30  
  Purchase #6 $157.77   9.432%   $172.6509   $172.65   $172.65   $172.70  
  Purchase #7 $168.91   4.703%   $176.8538   $176.85   $176.85   $176.90  
  7 purchase totals = $1,051.08       $1,126.7187   $1,126.71   $1,126.75   $1,126.70