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	$168.50	3.601%	$174.5677	$174.57	$174.55	$174.60
Purchase #2	$135.60	6.121%	$143.9001	$143.90	$143.90	$143.90
Purchase #3	$250.57	4.752%	$262.4771	$262.48	$262.50	$262.50
Purchase #4	$47.51	10.404%	$52.4529	$52.45	$52.45	$52.50
Purchase #5	$116.97	8.811%	$127.2762	$127.28	$127.30	$127.30
Purchase #6	$10.57	6.469%	$11.2538	$11.25	$11.25	$11.30
Purchase #7	$110.65	8.144%	$119.6613	$119.66	$119.65	$119.70
7 purchase totals =	$840.37		$891.5891	$891.59	$891.60	$891.80