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 $54.68   13.383%   $61.9978   $62.00   $62.00   $62.00  
  Purchase #2 $197.62   7.431%   $212.3051   $212.31   $212.30   $212.30  
  Purchase #3 $171.93   5.558%   $181.4859   $181.49   $181.50   $181.50  
  Purchase #4 $244.31   5.436%   $257.5907   $257.59   $257.60   $257.60  
  Purchase #5 $74.96   10.473%   $82.8106   $82.81   $82.80   $82.80  
  Purchase #6 $139.77   9.141%   $152.5464   $152.55   $152.55   $152.50  
  Purchase #7 $55.52   5.629%   $58.6452   $58.65   $58.65   $58.60  
  7 purchase totals = $938.79       $1,007.3817   $1,007.40   $1,007.40   $1,007.30