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 $209.29   6.695%   $223.302   $223.30   $223.30   $223.30  
  Purchase #2 $56.93   7.219%   $61.0398   $61.04   $61.05   $61.00  
  Purchase #3 $95.49   10.466%   $105.484   $105.48   $105.50   $105.50  
  Purchase #4 $110.95   7.814%   $119.6196   $119.62   $119.60   $119.60  
  Purchase #5 $147.28   9.831%   $161.7591   $161.76   $161.75   $161.80  
  Purchase #6 $232.53   3.231%   $240.043   $240.04   $240.05   $240.00  
  Purchase #7 $200.97   7.475%   $215.9925   $215.99   $216.00   $216.00  
  7 purchase totals = $1,053.44       $1,127.2400   $1,127.23   $1,127.25   $1,127.20