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 $202.97   5.386%   $213.902   $213.90   $213.90   $213.90  
  Purchase #2 $86.71   8.170%   $93.7942   $93.79   $93.80   $93.80  
  Purchase #3 $235.26   3.317%   $243.0636   $243.06   $243.05   $243.10  
  Purchase #4 $220.64   7.791%   $237.8301   $237.83   $237.85   $237.80  
  Purchase #5 $59.80   8.460%   $64.8591   $64.86   $64.85   $64.90  
  Purchase #6 $217.81   11.803%   $243.5181   $243.52   $243.50   $243.50  
  Purchase #7 $39.59   12.740%   $44.6338   $44.63   $44.65   $44.60  
  7 purchase totals = $1,062.78       $1,141.6009   $1,141.59   $1,141.60   $1,141.60