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 $170.48   7.239%   $182.821   $182.82   $182.80   $182.80  
  Purchase #2 $234.68   7.151%   $251.462   $251.46   $251.45   $251.50  
  Purchase #3 $190.99   3.487%   $197.6498   $197.65   $197.65   $197.60  
  Purchase #4 $192.32   4.177%   $200.3532   $200.35   $200.35   $200.40  
  Purchase #5 $248.98   5.320%   $262.2257   $262.23   $262.25   $262.20  
  Purchase #6 $31.53   12.651%   $35.5189   $35.52   $35.50   $35.50  
  Purchase #7 $66.78   12.464%   $75.1035   $75.10   $75.10   $75.10  
  7 purchase totals = $1,135.76       $1,205.1341   $1,205.13   $1,205.10   $1,205.10