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 $92.32   3.155%   $95.2327   $95.23   $95.25   $95.20  
  Purchase #2 $86.31   12.429%   $97.0375   $97.04   $97.05   $97.00  
  Purchase #3 $223.57   5.435%   $235.721   $235.72   $235.70   $235.70  
  Purchase #4 $190.25   4.653%   $199.1023   $199.10   $199.10   $199.10  
  Purchase #5 $201.44   4.749%   $211.0064   $211.01   $211.00   $211.00  
  Purchase #6 $198.35   11.573%   $221.305   $221.31   $221.30   $221.30  
  Purchase #7 $112.68   8.127%   $121.8375   $121.84   $121.85   $121.80  
  7 purchase totals = $1,104.92       $1,181.2424   $1,181.25   $1,181.25   $1,181.10