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 $84.71   13.223%   $95.9112   $95.91   $95.90   $95.90  
  Purchase #2 $106.84   5.597%   $112.8198   $112.82   $112.80   $112.80  
  Purchase #3 $184.91   8.384%   $200.4129   $200.41   $200.40   $200.40  
  Purchase #4 $212.83   11.865%   $238.0823   $238.08   $238.10   $238.10  
  Purchase #5 $33.95   5.850%   $35.9361   $35.94   $35.95   $35.90  
  Purchase #6 $235.26   7.243%   $252.2999   $252.30   $252.30   $252.30  
  Purchase #7 $152.47   11.350%   $169.7753   $169.78   $169.80   $169.80  
  7 purchase totals = $1,010.97       $1,105.2375   $1,105.24   $1,105.25   $1,105.20