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 $111.26   12.759%   $125.4557   $125.46   $125.45   $125.50  
  Purchase #2 $145.40   4.461%   $151.8863   $151.89   $151.90   $151.90  
  Purchase #3 $80.92   7.171%   $86.7228   $86.72   $86.70   $86.70  
  Purchase #4 $244.58   8.489%   $265.3424   $265.34   $265.35   $265.30  
  Purchase #5 $70.46   13.472%   $79.9524   $79.95   $79.95   $80.00  
  Purchase #6 $82.50   5.171%   $86.7661   $86.77   $86.75   $86.80  
  Purchase #7 $239.93   13.521%   $272.3709   $272.37   $272.35   $272.40  
  7 purchase totals = $975.05       $1,068.4966   $1,068.50   $1,068.45   $1,068.60