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 $180.62   8.425%   $195.8372   $195.84   $195.85   $195.80  
  Purchase #2 $31.87   9.859%   $35.0121   $35.01   $35.00   $35.00  
  Purchase #3 $148.35   11.212%   $164.983   $164.98   $165.00   $165.00  
  Purchase #4 $244.27   11.370%   $272.0435   $272.04   $272.05   $272.00  
  Purchase #5 $61.33   5.127%   $64.4744   $64.47   $64.45   $64.50  
  Purchase #6 $179.59   4.693%   $188.0182   $188.02   $188.00   $188.00  
  Purchase #7 $228.53   10.407%   $252.3131   $252.31   $252.30   $252.30  
  7 purchase totals = $1,074.56       $1,172.6815   $1,172.67   $1,172.65   $1,172.60