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 $48.65   5.852%   $51.497   $51.50   $51.50   $51.50  
  Purchase #2 $238.72   3.502%   $247.08   $247.08   $247.10   $247.10  
  Purchase #3 $151.58   7.123%   $162.377   $162.38   $162.40   $162.40  
  Purchase #4 $193.35   12.479%   $217.4781   $217.48   $217.50   $217.50  
  Purchase #5 $238.25   10.647%   $263.6165   $263.62   $263.60   $263.60  
  Purchase #6 $68.79   7.506%   $73.9534   $73.95   $73.95   $74.00  
  Purchase #7 $80.59   7.753%   $86.8381   $86.84   $86.85   $86.80  
  7 purchase totals = $1,019.93       $1,102.8401   $1,102.85   $1,102.90   $1,102.90