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 $175.95   11.506%   $196.1948   $196.19   $196.20   $196.20  
  Purchase #2 $43.39   3.456%   $44.8896   $44.89   $44.90   $44.90  
  Purchase #3 $191.76   6.193%   $203.6357   $203.64   $203.65   $203.60  
  Purchase #4 $120.29   6.274%   $127.837   $127.84   $127.85   $127.80  
  Purchase #5 $188.68   7.382%   $202.6084   $202.61   $202.60   $202.60  
  Purchase #6 $214.93   10.499%   $237.4955   $237.50   $237.50   $237.50  
  Purchase #7 $88.46   5.723%   $93.5226   $93.52   $93.50   $93.50  
  7 purchase totals = $1,023.46       $1,106.1836   $1,106.19   $1,106.20   $1,106.10