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 $195.59   4.655%   $204.6947   $204.69   $204.70   $204.70  
  Purchase #2 $86.56   11.344%   $96.3794   $96.38   $96.40   $96.40  
  Purchase #3 $244.42   13.752%   $278.0326   $278.03   $278.05   $278.00  
  Purchase #4 $62.94   13.628%   $71.5175   $71.52   $71.50   $71.50  
  Purchase #5 $226.71   11.412%   $252.5821   $252.58   $252.60   $252.60  
  Purchase #6 $248.47   11.732%   $277.6205   $277.62   $277.60   $277.60  
  Purchase #7 $38.77   13.402%   $43.966   $43.97   $43.95   $44.00  
  7 purchase totals = $1,103.46       $1,224.7928   $1,224.79   $1,224.80   $1,224.80