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 $98.86   7.283%   $106.06   $106.06   $106.05   $106.10  
  Purchase #2 $179.74   7.305%   $192.87   $192.87   $192.85   $192.90  
  Purchase #3 $164.87   7.276%   $176.8659   $176.87   $176.85   $176.90  
  Purchase #4 $168.36   9.415%   $184.2111   $184.21   $184.20   $184.20  
  Purchase #5 $208.43   10.190%   $229.669   $229.67   $229.65   $229.70  
  Purchase #6 $74.89   5.833%   $79.2583   $79.26   $79.25   $79.30  
  Purchase #7 $211.67   7.140%   $226.7832   $226.78   $226.80   $226.80  
  7 purchase totals = $1,106.82       $1,195.7175   $1,195.72   $1,195.65   $1,195.90