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 $61.76   10.415%   $68.1923   $68.19   $68.20   $68.20  
  Purchase #2 $185.70   10.149%   $204.5467   $204.55   $204.55   $204.50  
  Purchase #3 $190.86   5.776%   $201.8841   $201.88   $201.90   $201.90  
  Purchase #4 $186.36   6.620%   $198.697   $198.70   $198.70   $198.70  
  Purchase #5 $159.69   13.687%   $181.5468   $181.55   $181.55   $181.50  
  Purchase #6 $193.80   9.470%   $212.1529   $212.15   $212.15   $212.20  
  Purchase #7 $17.95   8.658%   $19.5041   $19.50   $19.50   $19.50  
  7 purchase totals = $996.12       $1,086.5239   $1,086.52   $1,086.55   $1,086.50