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 $207.26   9.793%   $227.557   $227.56   $227.55   $227.60  
  Purchase #2 $248.73   7.771%   $268.0588   $268.06   $268.05   $268.10  
  Purchase #3 $33.86   3.559%   $35.0651   $35.07   $35.05   $35.10  
  Purchase #4 $200.48   3.263%   $207.0217   $207.02   $207.00   $207.00  
  Purchase #5 $167.98   8.148%   $181.667   $181.67   $181.65   $181.70  
  Purchase #6 $137.40   4.204%   $143.1763   $143.18   $143.20   $143.20  
  Purchase #7 $21.75   5.171%   $22.8747   $22.87   $22.85   $22.90  
  7 purchase totals = $1,017.46       $1,085.4206   $1,085.43   $1,085.35   $1,085.60