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 $188.48   9.152%   $205.7297   $205.73   $205.75   $205.70  
  Purchase #2 $204.67   5.558%   $216.0456   $216.05   $216.05   $216.00  
  Purchase #3 $206.68   9.627%   $226.5771   $226.58   $226.60   $226.60  
  Purchase #4 $85.52   11.811%   $95.6208   $95.62   $95.60   $95.60  
  Purchase #5 $94.45   4.778%   $98.9628   $98.96   $98.95   $99.00  
  Purchase #6 $27.72   11.257%   $30.8404   $30.84   $30.85   $30.80  
  Purchase #7 $20.63   5.608%   $21.7869   $21.79   $21.80   $21.80  
  7 purchase totals = $828.15       $895.5633   $895.57   $895.60   $895.50