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 $211.58   5.532%   $223.2846   $223.28   $223.30   $223.30  
  Purchase #2 $143.71   8.247%   $155.5618   $155.56   $155.55   $155.60  
  Purchase #3 $207.72   7.792%   $223.9055   $223.91   $223.90   $223.90  
  Purchase #4 $234.75   5.575%   $247.8373   $247.84   $247.85   $247.80  
  Purchase #5 $231.40   10.629%   $255.9955   $256.00   $256.00   $256.00  
  Purchase #6 $83.26   4.469%   $86.9809   $86.98   $87.00   $87.00  
  Purchase #7 $242.96   5.569%   $256.4904   $256.49   $256.50   $256.50  
  7 purchase totals = $1,355.38       $1,450.0560   $1,450.06   $1,450.10   $1,450.10