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	$78.34	10.211%	$86.3393	$86.34	$86.35	$86.30
Purchase #2	$132.43	3.549%	$137.1299	$137.13	$137.15	$137.10
Purchase #3	$235.32	11.471%	$262.3136	$262.31	$262.30	$262.30
Purchase #4	$235.59	8.212%	$254.9367	$254.94	$254.95	$254.90
Purchase #5	$119.70	6.170%	$127.0855	$127.09	$127.10	$127.10
Purchase #6	$50.78	8.866%	$55.2822	$55.28	$55.30	$55.30
Purchase #7	$17.54	4.448%	$18.3202	$18.32	$18.30	$18.30
7 purchase totals =	$869.70		$941.4074	$941.41	$941.45	$941.30