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	$81.30	8.518%	$88.2251	$88.23	$88.25	$88.20
Purchase #2	$127.35	5.341%	$134.1518	$134.15	$134.15	$134.20
Purchase #3	$172.67	10.417%	$190.657	$190.66	$190.65	$190.70
Purchase #4	$102.46	10.429%	$113.1456	$113.15	$113.15	$113.10
Purchase #5	$227.84	9.387%	$249.2273	$249.23	$249.25	$249.20
Purchase #6	$115.78	9.771%	$127.0929	$127.09	$127.10	$127.10
Purchase #7	$174.94	10.731%	$193.7128	$193.71	$193.70	$193.70
7 purchase totals =	$1,002.34		$1,096.2125	$1,096.22	$1,096.25	$1,096.20