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 $58.70   5.381%   $61.8586   $61.86   $61.85   $61.90  
  Purchase #2 $218.98   5.797%   $231.6743   $231.67   $231.65   $231.70  
  Purchase #3 $200.49   7.870%   $216.2686   $216.27   $216.25   $216.30  
  Purchase #4 $59.32   4.617%   $62.0588   $62.06   $62.05   $62.10  
  Purchase #5 $34.74   5.595%   $36.6837   $36.68   $36.70   $36.70  
  Purchase #6 $189.53   11.751%   $211.8017   $211.80   $211.80   $211.80  
  Purchase #7 $232.82   5.250%   $245.0431   $245.04   $245.05   $245.00  
  7 purchase totals = $994.58       $1,065.3888   $1,065.38   $1,065.35   $1,065.50