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	$228.80	3.400%	$236.5792	$236.58	$236.60	$236.60
Purchase #2	$170.30	9.168%	$185.9131	$185.91	$185.90	$185.90
Purchase #3	$154.66	8.358%	$167.5865	$167.59	$167.60	$167.60
Purchase #4	$97.87	6.775%	$104.5007	$104.50	$104.50	$104.50
Purchase #5	$21.91	6.331%	$23.2971	$23.30	$23.30	$23.30
Purchase #6	$90.98	4.799%	$95.3461	$95.35	$95.35	$95.30
Purchase #7	$183.28	7.116%	$196.3222	$196.32	$196.30	$196.30
7 purchase totals =	$947.80		$1,009.5449	$1,009.55	$1,009.55	$1,009.50