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 $69.57   5.550%   $73.4311   $73.43   $73.45   $73.40  
  Purchase #2 $206.29   6.159%   $218.9954   $219.00   $219.00   $219.00  
  Purchase #3 $177.55   5.366%   $187.0773   $187.08   $187.10   $187.10  
  Purchase #4 $9.75   13.547%   $11.0708   $11.07   $11.05   $11.10  
  Purchase #5 $62.42   9.755%   $68.5091   $68.51   $68.50   $68.50  
  Purchase #6 $216.42   11.702%   $241.7455   $241.75   $241.75   $241.70  
  Purchase #7 $126.98   8.427%   $137.6806   $137.68   $137.70   $137.70  
  7 purchase totals = $868.98       $938.5098   $938.52   $938.55   $938.50