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 $62.28   5.251%   $65.5503   $65.55   $65.55   $65.60  
  Purchase #2 $217.58   7.637%   $234.1966   $234.20   $234.20   $234.20  
  Purchase #3 $49.45   7.238%   $53.0292   $53.03   $53.05   $53.00  
  Purchase #4 $127.60   10.366%   $140.827   $140.83   $140.85   $140.80  
  Purchase #5 $86.68   5.754%   $91.6676   $91.67   $91.65   $91.70  
  Purchase #6 $120.90   3.221%   $124.7942   $124.79   $124.80   $124.80  
  Purchase #7 $65.56   11.343%   $72.9965   $73.00   $73.00   $73.00  
  7 purchase totals = $730.05       $783.0614   $783.07   $783.10   $783.10