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 $188.85   10.120%   $207.9616   $207.96   $207.95   $208.00  
  Purchase #2 $147.95   5.496%   $156.0813   $156.08   $156.10   $156.10  
  Purchase #3 $151.77   5.195%   $159.6545   $159.65   $159.65   $159.70  
  Purchase #4 $54.73   3.552%   $56.674   $56.67   $56.65   $56.70  
  Purchase #5 $119.60   10.193%   $131.7908   $131.79   $131.80   $131.80  
  Purchase #6 $150.48   10.353%   $166.0592   $166.06   $166.05   $166.10  
  Purchase #7 $121.66   5.330%   $128.1445   $128.14   $128.15   $128.10  
  7 purchase totals = $935.04       $1,006.3659   $1,006.35   $1,006.35   $1,006.50