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 $87.66   7.250%   $94.0154   $94.02   $94.00   $94.00  
  Purchase #2 $15.28   13.700%   $17.3734   $17.37   $17.35   $17.40  
  Purchase #3 $239.46   9.437%   $262.0578   $262.06   $262.05   $262.10  
  Purchase #4 $25.37   5.238%   $26.6989   $26.70   $26.70   $26.70  
  Purchase #5 $231.81   5.568%   $244.7172   $244.72   $244.70   $244.70  
  Purchase #6 $165.82   11.568%   $185.0021   $185.00   $185.00   $185.00  
  Purchase #7 $226.66   5.406%   $238.9132   $238.91   $238.90   $238.90  
  7 purchase totals = $992.06       $1,068.7780   $1,068.78   $1,068.70   $1,068.80