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 $96.55   7.832%   $104.1118   $104.11   $104.10   $104.10  
  Purchase #2 $211.93   13.532%   $240.6084   $240.61   $240.60   $240.60  
  Purchase #3 $12.92   10.664%   $14.2978   $14.30   $14.30   $14.30  
  Purchase #4 $147.94   9.400%   $161.8464   $161.85   $161.85   $161.80  
  Purchase #5 $164.25   12.508%   $184.7944   $184.79   $184.80   $184.80  
  Purchase #6 $149.60   12.649%   $168.5229   $168.52   $168.50   $168.50  
  Purchase #7 $185.82   8.687%   $201.9622   $201.96   $201.95   $202.00  
  7 purchase totals = $969.01       $1,076.1439   $1,076.14   $1,076.10   $1,076.10