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 $204.62   11.367%   $227.8792   $227.88   $227.90   $227.90  
  Purchase #2 $185.38   10.561%   $204.958   $204.96   $204.95   $205.00  
  Purchase #3 $220.29   12.600%   $248.0465   $248.05   $248.05   $248.00  
  Purchase #4 $206.75   6.373%   $219.9262   $219.93   $219.95   $219.90  
  Purchase #5 $166.43   7.717%   $179.2734   $179.27   $179.25   $179.30  
  Purchase #6 $196.66   11.415%   $219.1087   $219.11   $219.10   $219.10  
  Purchase #7 $56.96   11.213%   $63.3469   $63.35   $63.35   $63.30  
  7 purchase totals = $1,237.09       $1,362.5389   $1,362.55   $1,362.55   $1,362.50