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 $208.73   4.371%   $217.8536   $217.85   $217.85   $217.90  
  Purchase #2 $22.94   12.450%   $25.796   $25.80   $25.80   $25.80  
  Purchase #3 $113.36   12.317%   $127.3226   $127.32   $127.30   $127.30  
  Purchase #4 $218.61   12.118%   $245.1012   $245.10   $245.10   $245.10  
  Purchase #5 $141.50   12.435%   $159.0955   $159.10   $159.10   $159.10  
  Purchase #6 $247.51   6.194%   $262.8408   $262.84   $262.85   $262.80  
  Purchase #7 $73.75   3.466%   $76.3062   $76.31   $76.30   $76.30  
  7 purchase totals = $1,026.40       $1,114.3159   $1,114.32   $1,114.30   $1,114.30