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	$165.27	4.405%	$172.5501	$172.55	$172.55	$172.60
Purchase #2	$19.74	11.222%	$21.9552	$21.96	$21.95	$22.00
Purchase #3	$138.78	12.720%	$156.4328	$156.43	$156.45	$156.40
Purchase #4	$156.88	11.180%	$174.4192	$174.42	$174.40	$174.40
Purchase #5	$180.80	9.651%	$198.249	$198.25	$198.25	$198.20
Purchase #6	$89.40	3.373%	$92.4155	$92.42	$92.40	$92.40
Purchase #7	$23.69	9.312%	$25.896	$25.90	$25.90	$25.90
7 purchase totals =	$774.56		$841.9178	$841.93	$841.90	$841.90