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 $152.85   7.162%   $163.7971   $163.80   $163.80   $163.80  
  Purchase #2 $184.54   5.483%   $194.6583   $194.66   $194.65   $194.70  
  Purchase #3 $78.79   10.355%   $86.9487   $86.95   $86.95   $86.90  
  Purchase #4 $192.59   7.481%   $206.9977   $207.00   $207.00   $207.00  
  Purchase #5 $48.52   12.778%   $54.7199   $54.72   $54.70   $54.70  
  Purchase #6 $212.57   10.650%   $235.2087   $235.21   $235.20   $235.20  
  Purchase #7 $74.73   8.129%   $80.8048   $80.80   $80.80   $80.80  
  7 purchase totals = $944.59       $1,023.1352   $1,023.14   $1,023.10   $1,023.10