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 $233.63   7.734%   $251.6989   $251.70   $251.70   $251.70  
  Purchase #2 $220.91   9.242%   $241.3265   $241.33   $241.35   $241.30  
  Purchase #3 $83.99   3.698%   $87.096   $87.10   $87.10   $87.10  
  Purchase #4 $123.29   3.663%   $127.8061   $127.81   $127.80   $127.80  
  Purchase #5 $104.80   6.846%   $111.9746   $111.97   $111.95   $112.00  
  Purchase #6 $217.79   7.561%   $234.2571   $234.26   $234.25   $234.30  
  Purchase #7 $98.86   8.707%   $107.4677   $107.47   $107.45   $107.50  
  7 purchase totals = $1,083.27       $1,161.6269   $1,161.64   $1,161.60   $1,161.70