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	$81.92	3.308%	$84.6299	$84.63	$84.65	$84.60
Purchase #2	$238.88	3.589%	$247.4534	$247.45	$247.45	$247.50
Purchase #3	$101.63	9.571%	$111.357	$111.36	$111.35	$111.40
Purchase #4	$110.63	11.448%	$123.2949	$123.29	$123.30	$123.30
Purchase #5	$138.48	11.579%	$154.5146	$154.51	$154.50	$154.50
Purchase #6	$209.40	12.460%	$235.4912	$235.49	$235.50	$235.50
Purchase #7	$54.64	11.699%	$61.0323	$61.03	$61.05	$61.00
7 purchase totals =	$935.58		$1,017.7733	$1,017.76	$1,017.80	$1,017.80