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 $235.49   3.834%   $244.5187   $244.52   $244.50   $244.50  
  Purchase #2 $223.43   10.252%   $246.336   $246.34   $246.35   $246.30  
  Purchase #3 $233.87   5.269%   $246.1926   $246.19   $246.20   $246.20  
  Purchase #4 $89.26   6.520%   $95.0798   $95.08   $95.10   $95.10  
  Purchase #5 $57.83   3.124%   $59.6366   $59.64   $59.65   $59.60  
  Purchase #6 $89.97   3.715%   $93.3124   $93.31   $93.30   $93.30  
  Purchase #7 $193.41   7.543%   $207.9989   $208.00   $208.00   $208.00  
  7 purchase totals = $1,123.26       $1,193.0750   $1,193.08   $1,193.10   $1,193.00