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	$167.73	6.258%	$178.2265	$178.23	$178.25	$178.20
Purchase #2	$55.71	6.552%	$59.3601	$59.36	$59.35	$59.40
Purchase #3	$201.59	3.823%	$209.2968	$209.30	$209.30	$209.30
Purchase #4	$241.45	13.820%	$274.8184	$274.82	$274.80	$274.80
Purchase #5	$153.33	5.589%	$161.8996	$161.90	$161.90	$161.90
Purchase #6	$14.94	6.493%	$15.9101	$15.91	$15.90	$15.90
Purchase #7	$139.84	3.455%	$144.6715	$144.67	$144.65	$144.70
7 purchase totals =	$974.59		$1,044.1830	$1,044.19	$1,044.15	$1,044.20