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 $34.64   4.253%   $36.1132   $36.11   $36.10   $36.10  
  Purchase #2 $106.28   11.658%   $118.6701   $118.67   $118.65   $118.70  
  Purchase #3 $220.73   10.740%   $244.4364   $244.44   $244.45   $244.40  
  Purchase #4 $76.32   13.695%   $86.772   $86.77   $86.75   $86.80  
  Purchase #5 $218.64   7.402%   $234.8237   $234.82   $234.80   $234.80  
  Purchase #6 $231.81   12.172%   $260.0259   $260.03   $260.05   $260.00  
  Purchase #7 $123.67   3.339%   $127.7993   $127.80   $127.80   $127.80  
  7 purchase totals = $1,012.09       $1,108.6406   $1,108.64   $1,108.60   $1,108.60