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	$218.38	9.120%	$238.2963	$238.30	$238.30	$238.30
Purchase #2	$172.93	4.630%	$180.9367	$180.94	$180.95	$180.90
Purchase #3	$6.81	4.289%	$7.1021	$7.10	$7.10	$7.10
Purchase #4	$248.57	7.237%	$266.559	$266.56	$266.55	$266.60
Purchase #5	$107.28	6.296%	$114.0343	$114.03	$114.05	$114.00
Purchase #6	$91.59	13.133%	$103.6185	$103.62	$103.60	$103.60
Purchase #7	$149.92	12.296%	$168.3542	$168.35	$168.35	$168.40
7 purchase totals =	$995.48		$1,078.9011	$1,078.90	$1,078.90	$1,078.90