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 $86.74   9.669%   $95.1269   $95.13   $95.15   $95.10  
  Purchase #2 $35.33   6.414%   $37.5961   $37.60   $37.60   $37.60  
  Purchase #3 $56.91   13.816%   $64.7727   $64.77   $64.75   $64.80  
  Purchase #4 $162.55   3.542%   $168.3075   $168.31   $168.30   $168.30  
  Purchase #5 $61.53   10.852%   $68.2072   $68.21   $68.20   $68.20  
  Purchase #6 $6.91   3.418%   $7.1462   $7.15   $7.15   $7.10  
  Purchase #7 $155.76   6.515%   $165.9078   $165.91   $165.90   $165.90  
  7 purchase totals = $565.73       $607.0644   $607.08   $607.05   $607.00