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 $125.64   12.816%   $141.742   $141.74   $141.75   $141.70  
  Purchase #2 $180.65   6.705%   $192.7626   $192.76   $192.75   $192.80  
  Purchase #3 $204.84   10.454%   $226.254   $226.25   $226.25   $226.30  
  Purchase #4 $143.95   3.560%   $149.0746   $149.07   $149.05   $149.10  
  Purchase #5 $99.84   3.723%   $103.557   $103.56   $103.55   $103.60  
  Purchase #6 $200.82   7.187%   $215.2529   $215.25   $215.25   $215.30  
  Purchase #7 $212.75   9.437%   $232.8272   $232.83   $232.85   $232.80  
  7 purchase totals = $1,168.49       $1,261.4703   $1,261.46   $1,261.45   $1,261.60