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 $118.62   7.118%   $127.0634   $127.06   $127.05   $127.10  
  Purchase #2 $249.42   9.171%   $272.2943   $272.29   $272.30   $272.30  
  Purchase #3 $42.67   8.199%   $46.1685   $46.17   $46.15   $46.20  
  Purchase #4 $200.74   12.622%   $226.0774   $226.08   $226.10   $226.10  
  Purchase #5 $226.82   4.734%   $237.5577   $237.56   $237.55   $237.60  
  Purchase #6 $67.77   6.632%   $72.2645   $72.26   $72.25   $72.30  
  Purchase #7 $47.97   6.202%   $50.9451   $50.95   $50.95   $50.90  
  7 purchase totals = $954.01       $1,032.3709   $1,032.37   $1,032.35   $1,032.50