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 $212.89   10.433%   $235.1008   $235.10   $235.10   $235.10  
  Purchase #2 $41.40   8.140%   $44.77   $44.77   $44.75   $44.80  
  Purchase #3 $186.34   12.161%   $209.0008   $209.00   $209.00   $209.00  
  Purchase #4 $219.70   10.261%   $242.2434   $242.24   $242.25   $242.20  
  Purchase #5 $169.72   8.428%   $184.024   $184.02   $184.00   $184.00  
  Purchase #6 $208.65   7.731%   $224.7807   $224.78   $224.80   $224.80  
  Purchase #7 $203.73   10.737%   $225.6045   $225.60   $225.60   $225.60  
  7 purchase totals = $1,242.43       $1,365.5242   $1,365.51   $1,365.50   $1,365.50