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 $92.67   13.426%   $105.1119   $105.11   $105.10   $105.10  
  Purchase #2 $232.77   6.673%   $248.3027   $248.30   $248.30   $248.30  
  Purchase #3 $179.28   8.585%   $194.6712   $194.67   $194.65   $194.70  
  Purchase #4 $150.56   8.409%   $163.2206   $163.22   $163.20   $163.20  
  Purchase #5 $219.92   9.859%   $241.6019   $241.60   $241.60   $241.60  
  Purchase #6 $48.34   10.563%   $53.4462   $53.45   $53.45   $53.40  
  Purchase #7 $189.51   11.647%   $211.5822   $211.58   $211.60   $211.60  
  7 purchase totals = $1,113.05       $1,217.9367   $1,217.93   $1,217.90   $1,217.90