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 $61.52   4.594%   $64.3462   $64.35   $64.35   $64.30  
  Purchase #2 $60.45   11.379%   $67.3286   $67.33   $67.35   $67.30  
  Purchase #3 $172.64   6.830%   $184.4313   $184.43   $184.45   $184.40  
  Purchase #4 $196.81   5.268%   $207.178   $207.18   $207.20   $207.20  
  Purchase #5 $10.41   7.409%   $11.1813   $11.18   $11.20   $11.20  
  Purchase #6 $214.67   7.705%   $231.2103   $231.21   $231.20   $231.20  
  Purchase #7 $245.41   7.439%   $263.666   $263.67   $263.65   $263.70  
  7 purchase totals = $961.91       $1,029.3417   $1,029.35   $1,029.40   $1,029.30