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 $77.89   11.357%   $86.736   $86.74   $86.75   $86.70  
  Purchase #2 $213.81   5.700%   $225.9972   $226.00   $226.00   $226.00  
  Purchase #3 $108.78   8.780%   $118.3309   $118.33   $118.35   $118.30  
  Purchase #4 $241.86   8.855%   $263.2767   $263.28   $263.30   $263.30  
  Purchase #5 $187.91   10.450%   $207.5466   $207.55   $207.55   $207.50  
  Purchase #6 $195.53   7.852%   $210.883   $210.88   $210.90   $210.90  
  Purchase #7 $114.98   7.869%   $124.0278   $124.03   $124.05   $124.00  
  7 purchase totals = $1,140.76       $1,236.7982   $1,236.81   $1,236.90   $1,236.70