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 $205.27   13.320%   $232.612   $232.61   $232.60   $232.60  
  Purchase #2 $153.51   11.690%   $171.4553   $171.46   $171.45   $171.50  
  Purchase #3 $192.53   11.488%   $214.6478   $214.65   $214.65   $214.60  
  Purchase #4 $215.58   13.217%   $244.0732   $244.07   $244.05   $244.10  
  Purchase #5 $155.64   7.716%   $167.6492   $167.65   $167.65   $167.60  
  Purchase #6 $167.68   5.269%   $176.5151   $176.52   $176.50   $176.50  
  Purchase #7 $36.92   12.869%   $41.6712   $41.67   $41.65   $41.70  
  7 purchase totals = $1,127.13       $1,248.6238   $1,248.63   $1,248.55   $1,248.60