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 $176.58   10.220%   $194.6265   $194.63   $194.65   $194.60  
  Purchase #2 $233.51   3.404%   $241.4587   $241.46   $241.45   $241.50  
  Purchase #3 $234.69   7.515%   $252.327   $252.33   $252.35   $252.30  
  Purchase #4 $74.79   3.207%   $77.1885   $77.19   $77.20   $77.20  
  Purchase #5 $116.40   7.367%   $124.9752   $124.98   $125.00   $125.00  
  Purchase #6 $124.44   10.858%   $137.9517   $137.95   $137.95   $138.00  
  Purchase #7 $59.33   11.263%   $66.0123   $66.01   $66.00   $66.00  
  7 purchase totals = $1,019.74       $1,094.5399   $1,094.55   $1,094.60   $1,094.60