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	$236.35	11.256%	$262.9536	$262.95	$262.95	$263.00
Purchase #2	$88.89	4.111%	$92.5443	$92.54	$92.55	$92.50
Purchase #3	$107.41	4.431%	$112.1693	$112.17	$112.15	$112.20
Purchase #4	$192.61	4.801%	$201.8572	$201.86	$201.85	$201.90
Purchase #5	$230.46	6.271%	$244.9121	$244.91	$244.90	$244.90
Purchase #6	$19.80	4.585%	$20.7078	$20.71	$20.70	$20.70
Purchase #7	$139.41	5.639%	$147.2713	$147.27	$147.25	$147.30
7 purchase totals =	$1,014.93		$1,082.4156	$1,082.41	$1,082.35	$1,082.50