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 $215.88   13.350%   $244.7   $244.70   $244.70   $244.70  
  Purchase #2 $55.92   6.627%   $59.6258   $59.63   $59.65   $59.60  
  Purchase #3 $185.40   8.564%   $201.2777   $201.28   $201.30   $201.30  
  Purchase #4 $84.85   8.453%   $92.0224   $92.02   $92.00   $92.00  
  Purchase #5 $115.79   5.874%   $122.5915   $122.59   $122.60   $122.60  
  Purchase #6 $192.52   12.691%   $216.9527   $216.95   $216.95   $217.00  
  Purchase #7 $219.41   11.415%   $244.4557   $244.46   $244.45   $244.50  
  7 purchase totals = $1,069.77       $1,181.6258   $1,181.63   $1,181.65   $1,181.70