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	$242.42	8.268%	$262.4633	$262.46	$262.45	$262.50
Purchase #2	$134.82	6.267%	$143.2692	$143.27	$143.25	$143.30
Purchase #3	$81.78	10.496%	$90.3636	$90.36	$90.35	$90.40
Purchase #4	$116.89	8.694%	$127.0524	$127.05	$127.05	$127.10
Purchase #5	$229.63	3.656%	$238.0253	$238.03	$238.05	$238.00
Purchase #6	$131.74	8.435%	$142.8523	$142.85	$142.85	$142.90
Purchase #7	$150.91	11.745%	$168.6344	$168.63	$168.65	$168.60
7 purchase totals =	$1,088.19		$1,172.6605	$1,172.65	$1,172.65	$1,172.80