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 $96.60   5.545%   $101.9565   $101.96   $101.95   $102.00  
  Purchase #2 $70.28   9.661%   $77.0698   $77.07   $77.05   $77.10  
  Purchase #3 $164.25   4.568%   $171.7529   $171.75   $171.75   $171.80  
  Purchase #4 $218.99   11.106%   $243.311   $243.31   $243.30   $243.30  
  Purchase #5 $233.66   3.363%   $241.518   $241.52   $241.50   $241.50  
  Purchase #6 $199.72   8.474%   $216.6443   $216.64   $216.65   $216.60  
  Purchase #7 $38.43   12.329%   $43.168   $43.17   $43.15   $43.20  
  7 purchase totals = $1,021.93       $1,095.4205   $1,095.42   $1,095.35   $1,095.50