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 $60.41   7.758%   $65.0966   $65.10   $65.10   $65.10  
  Purchase #2 $244.50   9.701%   $268.2189   $268.22   $268.20   $268.20  
  Purchase #3 $5.31   7.654%   $5.7164   $5.72   $5.70   $5.70  
  Purchase #4 $228.33   3.166%   $235.5589   $235.56   $235.55   $235.60  
  Purchase #5 $131.83   13.810%   $150.0357   $150.04   $150.05   $150.00  
  Purchase #6 $50.47   3.473%   $52.2228   $52.22   $52.20   $52.20  
  Purchase #7 $205.52   6.186%   $218.2335   $218.23   $218.25   $218.20  
  7 purchase totals = $926.37       $995.0828   $995.09   $995.05   $995.00