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	$174.61	4.467%	$182.4098	$182.41	$182.40	$182.40
Purchase #2	$81.42	13.600%	$92.4931	$92.49	$92.50	$92.50
Purchase #3	$123.78	13.741%	$140.7886	$140.79	$140.80	$140.80
Purchase #4	$50.87	8.670%	$55.2804	$55.28	$55.30	$55.30
Purchase #5	$82.97	9.210%	$90.6115	$90.61	$90.60	$90.60
Purchase #6	$190.52	10.796%	$211.0885	$211.09	$211.10	$211.10
Purchase #7	$226.38	4.797%	$237.2394	$237.24	$237.25	$237.20
7 purchase totals =	$930.55		$1,009.9113	$1,009.91	$1,009.95	$1,009.90