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 $62.90   6.548%   $67.0187   $67.02   $67.00   $67.00  
  Purchase #2 $30.32   5.554%   $32.004   $32.00   $32.00   $32.00  
  Purchase #3 $47.84   13.223%   $54.1659   $54.17   $54.15   $54.20  
  Purchase #4 $202.71   13.726%   $230.534   $230.53   $230.55   $230.50  
  Purchase #5 $216.58   6.747%   $231.1927   $231.19   $231.20   $231.20  
  Purchase #6 $184.94   4.110%   $192.541   $192.54   $192.55   $192.50  
  Purchase #7 $77.76   11.279%   $86.5306   $86.53   $86.55   $86.50  
  7 purchase totals = $823.05       $893.9869   $893.98   $894.00   $893.90