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 $200.86   8.701%   $218.3368   $218.34   $218.35   $218.30  
  Purchase #2 $107.92   8.826%   $117.445   $117.45   $117.45   $117.40  
  Purchase #3 $230.70   4.158%   $240.2925   $240.29   $240.30   $240.30  
  Purchase #4 $55.95   11.615%   $62.4486   $62.45   $62.45   $62.40  
  Purchase #5 $243.52   7.852%   $262.6412   $262.64   $262.65   $262.60  
  Purchase #6 $166.98   11.767%   $186.6285   $186.63   $186.65   $186.60  
  Purchase #7 $13.43   7.327%   $14.414   $14.41   $14.40   $14.40  
  7 purchase totals = $1,019.36       $1,102.2066   $1,102.21   $1,102.25   $1,102.00