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 $87.97   8.531%   $95.4747   $95.47   $95.45   $95.50  
  Purchase #2 $196.71   7.374%   $211.2154   $211.22   $211.20   $211.20  
  Purchase #3 $248.72   7.401%   $267.1278   $267.13   $267.15   $267.10  
  Purchase #4 $239.54   3.700%   $248.403   $248.40   $248.40   $248.40  
  Purchase #5 $169.36   12.362%   $190.2963   $190.30   $190.30   $190.30  
  Purchase #6 $25.58   11.110%   $28.4219   $28.42   $28.40   $28.40  
  Purchase #7 $109.68   10.343%   $121.0242   $121.02   $121.00   $121.00  
  7 purchase totals = $1,077.56       $1,161.9633   $1,161.96   $1,161.90   $1,161.90