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 $188.34   10.753%   $208.5922   $208.59   $208.60   $208.60  
  Purchase #2 $160.75   12.609%   $181.019   $181.02   $181.00   $181.00  
  Purchase #3 $62.98   7.837%   $67.9157   $67.92   $67.90   $67.90  
  Purchase #4 $223.69   7.770%   $241.0707   $241.07   $241.05   $241.10  
  Purchase #5 $114.51   6.609%   $122.078   $122.08   $122.10   $122.10  
  Purchase #6 $141.26   9.642%   $154.8803   $154.88   $154.90   $154.90  
  Purchase #7 $52.96   7.594%   $56.9818   $56.98   $57.00   $57.00  
  7 purchase totals = $944.49       $1,032.5377   $1,032.54   $1,032.55   $1,032.60