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 $183.43   5.249%   $193.0582   $193.06   $193.05   $193.10  
  Purchase #2 $204.86   3.362%   $211.7474   $211.75   $211.75   $211.70  
  Purchase #3 $74.27   5.260%   $78.1766   $78.18   $78.20   $78.20  
  Purchase #4 $167.62   12.761%   $189.01   $189.01   $189.00   $189.00  
  Purchase #5 $183.46   8.786%   $199.5788   $199.58   $199.60   $199.60  
  Purchase #6 $206.85   3.708%   $214.52   $214.52   $214.50   $214.50  
  Purchase #7 $186.72   11.817%   $208.7847   $208.78   $208.80   $208.80  
  7 purchase totals = $1,207.21       $1,294.8757   $1,294.88   $1,294.90   $1,294.90