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 $224.96   5.553%   $237.452   $237.45   $237.45   $237.50  
  Purchase #2 $110.35   7.566%   $118.6991   $118.70   $118.70   $118.70  
  Purchase #3 $148.32   7.850%   $159.9631   $159.96   $159.95   $160.00  
  Purchase #4 $198.81   6.527%   $211.7863   $211.79   $211.80   $211.80  
  Purchase #5 $87.57   9.799%   $96.151   $96.15   $96.15   $96.20  
  Purchase #6 $201.81   13.449%   $228.9514   $228.95   $228.95   $229.00  
  Purchase #7 $146.40   3.794%   $151.9544   $151.95   $151.95   $152.00  
  7 purchase totals = $1,118.22       $1,204.9573   $1,204.95   $1,204.95   $1,205.20