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 $214.25   6.431%   $228.0284   $228.03   $228.05   $228.00  
  Purchase #2 $226.93   12.448%   $255.1782   $255.18   $255.20   $255.20  
  Purchase #3 $62.34   9.636%   $68.3471   $68.35   $68.35   $68.30  
  Purchase #4 $216.25   6.633%   $230.5939   $230.59   $230.60   $230.60  
  Purchase #5 $144.60   13.867%   $164.6517   $164.65   $164.65   $164.70  
  Purchase #6 $193.87   5.732%   $204.9826   $204.98   $205.00   $205.00  
  Purchase #7 $223.60   9.271%   $244.33   $244.33   $244.35   $244.30  
  7 purchase totals = $1,281.84       $1,396.1119   $1,396.11   $1,396.20   $1,396.10