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 $87.36   6.562%   $93.0926   $93.09   $93.10   $93.10  
  Purchase #2 $98.96   4.437%   $103.3509   $103.35   $103.35   $103.40  
  Purchase #3 $207.68   13.349%   $235.4032   $235.40   $235.40   $235.40  
  Purchase #4 $156.87   8.477%   $170.1679   $170.17   $170.15   $170.20  
  Purchase #5 $202.83   11.779%   $226.7213   $226.72   $226.70   $226.70  
  Purchase #6 $167.57   11.125%   $186.2122   $186.21   $186.20   $186.20  
  Purchase #7 $102.77   7.603%   $110.5836   $110.58   $110.60   $110.60  
  7 purchase totals = $1,024.04       $1,125.5317   $1,125.52   $1,125.50   $1,125.60