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 $187.31   9.245%   $204.6268   $204.63   $204.65   $204.60  
  Purchase #2 $232.69   13.250%   $263.5214   $263.52   $263.50   $263.50  
  Purchase #3 $173.83   10.725%   $192.4733   $192.47   $192.45   $192.50  
  Purchase #4 $43.88   13.313%   $49.7217   $49.72   $49.70   $49.70  
  Purchase #5 $194.96   8.493%   $211.518   $211.52   $211.50   $211.50  
  Purchase #6 $191.69   6.276%   $203.7205   $203.72   $203.70   $203.70  
  Purchase #7 $22.95   4.228%   $23.9203   $23.92   $23.90   $23.90  
  7 purchase totals = $1,047.31       $1,149.5020   $1,149.50   $1,149.40   $1,149.40