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 $213.68   10.230%   $235.5395   $235.54   $235.55   $235.50  
  Purchase #2 $199.38   6.333%   $212.0067   $212.01   $212.00   $212.00  
  Purchase #3 $179.68   11.640%   $200.5948   $200.59   $200.60   $200.60  
  Purchase #4 $56.52   12.260%   $63.4494   $63.45   $63.45   $63.40  
  Purchase #5 $249.63   13.407%   $283.0979   $283.10   $283.10   $283.10  
  Purchase #6 $193.45   9.122%   $211.0965   $211.10   $211.10   $211.10  
  Purchase #7 $241.57   10.145%   $266.0773   $266.08   $266.10   $266.10  
  7 purchase totals = $1,333.91       $1,471.8621   $1,471.87   $1,471.90   $1,471.80