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	$245.76	10.601%	$271.813	$271.81	$271.80	$271.80
Purchase #2	$45.39	8.842%	$49.4034	$49.40	$49.40	$49.40
Purchase #3	$96.78	3.448%	$100.117	$100.12	$100.10	$100.10
Purchase #4	$93.79	5.551%	$98.9963	$99.00	$99.00	$99.00
Purchase #5	$13.86	4.640%	$14.5031	$14.50	$14.50	$14.50
Purchase #6	$52.49	9.516%	$57.4849	$57.48	$57.50	$57.50
Purchase #7	$84.71	6.593%	$90.2949	$90.29	$90.30	$90.30
7 purchase totals =	$632.78		$682.6126	$682.60	$682.60	$682.60