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 $195.71   9.721%   $214.735   $214.74   $214.75   $214.70  
  Purchase #2 $91.54   12.482%   $102.966   $102.97   $102.95   $103.00  
  Purchase #3 $238.25   13.196%   $269.6895   $269.69   $269.70   $269.70  
  Purchase #4 $172.65   9.799%   $189.568   $189.57   $189.55   $189.60  
  Purchase #5 $232.60   5.604%   $245.6349   $245.63   $245.65   $245.60  
  Purchase #6 $39.74   9.812%   $43.6393   $43.64   $43.65   $43.60  
  Purchase #7 $44.32   9.170%   $48.3841   $48.38   $48.40   $48.40  
  7 purchase totals = $1,014.81       $1,114.6168   $1,114.62   $1,114.65   $1,114.60