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 $212.93   10.810%   $235.9477   $235.95   $235.95   $235.90  
  Purchase #2 $166.53   13.709%   $189.3596   $189.36   $189.35   $189.40  
  Purchase #3 $50.66   12.701%   $57.0943   $57.09   $57.10   $57.10  
  Purchase #4 $148.58   7.248%   $159.3491   $159.35   $159.35   $159.30  
  Purchase #5 $244.74   4.372%   $255.44   $255.44   $255.45   $255.40  
  Purchase #6 $202.46   10.471%   $223.6596   $223.66   $223.65   $223.70  
  Purchase #7 $69.65   12.626%   $78.444   $78.44   $78.45   $78.40  
  7 purchase totals = $1,095.55       $1,199.2943   $1,199.29   $1,199.30   $1,199.20