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 $59.68   5.651%   $63.0525   $63.05   $63.05   $63.10  
  Purchase #2 $113.32   3.126%   $116.8624   $116.86   $116.85   $116.90  
  Purchase #3 $191.45   13.853%   $217.9716   $217.97   $217.95   $218.00  
  Purchase #4 $168.79   11.169%   $187.6422   $187.64   $187.65   $187.60  
  Purchase #5 $145.75   12.718%   $164.2865   $164.29   $164.30   $164.30  
  Purchase #6 $193.27   4.165%   $201.3197   $201.32   $201.30   $201.30  
  Purchase #7 $120.47   5.714%   $127.3537   $127.35   $127.35   $127.40  
  7 purchase totals = $992.73       $1,078.4886   $1,078.48   $1,078.45   $1,078.60