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 $53.98   13.173%   $61.0908   $61.09   $61.10   $61.10  
  Purchase #2 $80.51   6.106%   $85.4259   $85.43   $85.45   $85.40  
  Purchase #3 $150.59   3.128%   $155.3005   $155.30   $155.30   $155.30  
  Purchase #4 $114.89   11.171%   $127.7244   $127.72   $127.70   $127.70  
  Purchase #5 $240.74   11.856%   $269.2821   $269.28   $269.30   $269.30  
  Purchase #6 $189.73   6.280%   $201.645   $201.65   $201.65   $201.60  
  Purchase #7 $154.93   5.240%   $163.0483   $163.05   $163.05   $163.00  
  7 purchase totals = $985.37       $1,063.5170   $1,063.52   $1,063.55   $1,063.40