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 $71.42   3.415%   $73.859   $73.86   $73.85   $73.90  
  Purchase #2 $78.95   7.451%   $84.8326   $84.83   $84.85   $84.80  
  Purchase #3 $80.53   7.611%   $86.6591   $86.66   $86.65   $86.70  
  Purchase #4 $141.81   6.380%   $150.8575   $150.86   $150.85   $150.90  
  Purchase #5 $109.79   11.244%   $122.1348   $122.13   $122.15   $122.10  
  Purchase #6 $190.54   10.110%   $209.8036   $209.80   $209.80   $209.80  
  Purchase #7 $201.60   12.363%   $226.5238   $226.52   $226.50   $226.50  
  7 purchase totals = $874.64       $954.6704   $954.66   $954.65   $954.70