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 $97.32   5.164%   $102.3456   $102.35   $102.35   $102.30  
  Purchase #2 $44.85   5.471%   $47.3037   $47.30   $47.30   $47.30  
  Purchase #3 $88.61   5.533%   $93.5128   $93.51   $93.50   $93.50  
  Purchase #4 $147.76   13.482%   $167.681   $167.68   $167.70   $167.70  
  Purchase #5 $22.33   7.377%   $23.9773   $23.98   $24.00   $24.00  
  Purchase #6 $240.33   8.180%   $259.989   $259.99   $260.00   $260.00  
  Purchase #7 $66.26   9.356%   $72.4593   $72.46   $72.45   $72.50  
  7 purchase totals = $707.46       $767.2687   $767.27   $767.30   $767.30