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	$164.84	4.632%	$172.4754	$172.48	$172.50	$172.50
Purchase #2	$145.72	11.480%	$162.4487	$162.45	$162.45	$162.40
Purchase #3	$55.97	6.825%	$59.79	$59.79	$59.80	$59.80
Purchase #4	$93.88	10.693%	$103.9186	$103.92	$103.90	$103.90
Purchase #5	$215.44	9.629%	$236.1847	$236.18	$236.20	$236.20
Purchase #6	$222.90	3.828%	$231.4326	$231.43	$231.45	$231.40
Purchase #7	$10.73	13.377%	$12.1654	$12.17	$12.15	$12.20
7 purchase totals =	$909.48		$978.4154	$978.42	$978.45	$978.40