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 $101.39   6.142%   $107.6174   $107.62   $107.60   $107.60  
  Purchase #2 $165.96   5.862%   $175.6886   $175.69   $175.70   $175.70  
  Purchase #3 $71.64   7.348%   $76.9041   $76.90   $76.90   $76.90  
  Purchase #4 $94.52   8.839%   $102.8746   $102.87   $102.85   $102.90  
  Purchase #5 $235.35   3.474%   $243.5261   $243.53   $243.55   $243.50  
  Purchase #6 $241.33   8.620%   $262.1326   $262.13   $262.15   $262.10  
  Purchase #7 $192.60   3.795%   $199.9092   $199.91   $199.90   $199.90  
  7 purchase totals = $1,102.79       $1,168.6526   $1,168.65   $1,168.65   $1,168.60