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	$128.69	12.650%	$144.9693	$144.97	$144.95	$145.00
Purchase #2	$50.41	8.768%	$54.8299	$54.83	$54.85	$54.80
Purchase #3	$12.29	13.496%	$13.9487	$13.95	$13.95	$13.90
Purchase #4	$70.72	9.569%	$77.4872	$77.49	$77.50	$77.50
Purchase #5	$31.62	12.127%	$35.4546	$35.45	$35.45	$35.50
Purchase #6	$119.35	3.360%	$123.3602	$123.36	$123.35	$123.40
Purchase #7	$101.62	12.320%	$114.1396	$114.14	$114.15	$114.10
7 purchase totals =	$514.70		$564.1895	$564.19	$564.20	$564.20