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 $186.55   4.553%   $195.0436   $195.04   $195.05   $195.00  
  Purchase #2 $150.61   12.690%   $169.7224   $169.72   $169.70   $169.70  
  Purchase #3 $110.28   6.746%   $117.7195   $117.72   $117.70   $117.70  
  Purchase #4 $24.61   8.256%   $26.6418   $26.64   $26.65   $26.60  
  Purchase #5 $213.92   7.658%   $230.302   $230.30   $230.30   $230.30  
  Purchase #6 $86.84   13.142%   $98.2525   $98.25   $98.25   $98.30  
  Purchase #7 $206.49   12.496%   $232.293   $232.29   $232.30   $232.30  
  7 purchase totals = $979.30       $1,069.9748   $1,069.96   $1,069.95   $1,069.90