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 $183.38   10.294%   $202.2571   $202.26   $202.25   $202.30  
  Purchase #2 $45.97   7.217%   $49.2877   $49.29   $49.30   $49.30  
  Purchase #3 $162.32   10.347%   $179.1153   $179.12   $179.10   $179.10  
  Purchase #4 $131.41   12.123%   $147.3408   $147.34   $147.35   $147.30  
  Purchase #5 $49.93   3.650%   $51.7524   $51.75   $51.75   $51.80  
  Purchase #6 $193.27   3.789%   $200.593   $200.59   $200.60   $200.60  
  Purchase #7 $173.55   6.171%   $184.2598   $184.26   $184.25   $184.30  
  7 purchase totals = $939.83       $1,014.6061   $1,014.61   $1,014.60   $1,014.70