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 $177.42   9.619%   $194.486   $194.49   $194.50   $194.50  
  Purchase #2 $124.45   8.434%   $134.9461   $134.95   $134.95   $134.90  
  Purchase #3 $94.93   8.225%   $102.738   $102.74   $102.75   $102.70  
  Purchase #4 $122.59   9.239%   $133.9161   $133.92   $133.90   $133.90  
  Purchase #5 $15.36   4.221%   $16.0083   $16.01   $16.00   $16.00  
  Purchase #6 $249.59   7.637%   $268.6512   $268.65   $268.65   $268.70  
  Purchase #7 $152.92   12.590%   $172.1726   $172.17   $172.15   $172.20  
  7 purchase totals = $937.26       $1,022.9183   $1,022.93   $1,022.90   $1,022.90