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	$213.38	3.842%	$221.5781	$221.58	$221.60	$221.60
Purchase #2	$98.83	3.397%	$102.1873	$102.19	$102.20	$102.20
Purchase #3	$159.97	12.371%	$179.7599	$179.76	$179.75	$179.80
Purchase #4	$196.50	3.558%	$203.4915	$203.49	$203.50	$203.50
Purchase #5	$113.50	12.114%	$127.2494	$127.25	$127.25	$127.20
Purchase #6	$54.91	6.748%	$58.6153	$58.62	$58.60	$58.60
Purchase #7	$39.54	3.531%	$40.9362	$40.94	$40.95	$40.90
7 purchase totals =	$876.63		$933.8177	$933.83	$933.85	$933.80