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	$163.68	4.693%	$171.3615	$171.36	$171.35	$171.40
Purchase #2	$145.29	9.789%	$159.5124	$159.51	$159.50	$159.50
Purchase #3	$130.99	10.109%	$144.2318	$144.23	$144.25	$144.20
Purchase #4	$75.55	3.721%	$78.3612	$78.36	$78.35	$78.40
Purchase #5	$22.94	12.236%	$25.7469	$25.75	$25.75	$25.70
Purchase #6	$123.57	4.156%	$128.7056	$128.71	$128.70	$128.70
Purchase #7	$31.29	7.169%	$33.5332	$33.53	$33.55	$33.50
7 purchase totals =	$693.31		$741.4526	$741.45	$741.45	$741.40