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 $192.41   4.456%   $200.9838   $200.98   $201.00   $201.00  
  Purchase #2 $95.59   8.235%   $103.4618   $103.46   $103.45   $103.50  
  Purchase #3 $119.52   12.696%   $134.6943   $134.69   $134.70   $134.70  
  Purchase #4 $202.85   4.467%   $211.9113   $211.91   $211.90   $211.90  
  Purchase #5 $181.31   6.320%   $192.7688   $192.77   $192.75   $192.80  
  Purchase #6 $69.82   3.431%   $72.2155   $72.22   $72.20   $72.20  
  Purchase #7 $204.70   13.321%   $231.9681   $231.97   $231.95   $232.00  
  7 purchase totals = $1,066.20       $1,148.0036   $1,148.00   $1,147.95   $1,148.10