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 $240.40   9.283%   $262.7163   $262.72   $262.70   $262.70  
  Purchase #2 $63.68   11.835%   $71.2165   $71.22   $71.20   $71.20  
  Purchase #3 $138.54   7.692%   $149.1965   $149.20   $149.20   $149.20  
  Purchase #4 $125.70   11.315%   $139.923   $139.92   $139.90   $139.90  
  Purchase #5 $130.65   5.852%   $138.2956   $138.30   $138.30   $138.30  
  Purchase #6 $110.69   8.674%   $120.2913   $120.29   $120.30   $120.30  
  Purchase #7 $165.69   9.299%   $181.0975   $181.10   $181.10   $181.10  
  7 purchase totals = $975.35       $1,062.7367   $1,062.75   $1,062.70   $1,062.70