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 $212.44   5.747%   $224.6489   $224.65   $224.65   $224.60  
  Purchase #2 $211.43   9.106%   $230.6828   $230.68   $230.70   $230.70  
  Purchase #3 $132.48   11.561%   $147.796   $147.80   $147.80   $147.80  
  Purchase #4 $92.25   5.713%   $97.5202   $97.52   $97.50   $97.50  
  Purchase #5 $176.85   4.245%   $184.3573   $184.36   $184.35   $184.40  
  Purchase #6 $27.66   7.285%   $29.675   $29.68   $29.70   $29.70  
  Purchase #7 $112.35   6.140%   $119.2483   $119.25   $119.25   $119.20  
  7 purchase totals = $965.46       $1,033.9285   $1,033.94   $1,033.95   $1,033.90