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 $152.85   8.107%   $165.2415   $165.24   $165.25   $165.20  
  Purchase #2 $184.49   11.704%   $206.0827   $206.08   $206.10   $206.10  
  Purchase #3 $126.36   9.182%   $137.9624   $137.96   $137.95   $138.00  
  Purchase #4 $136.50   6.333%   $145.1445   $145.14   $145.15   $145.10  
  Purchase #5 $84.76   13.265%   $96.0034   $96.00   $96.00   $96.00  
  Purchase #6 $236.87   13.346%   $268.4827   $268.48   $268.50   $268.50  
  Purchase #7 $30.94   8.543%   $33.5832   $33.58   $33.60   $33.60  
  7 purchase totals = $952.77       $1,052.5004   $1,052.48   $1,052.55   $1,052.50