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	$185.95	6.844%	$198.6764	$198.68	$198.70	$198.70
Purchase #2	$90.71	12.324%	$101.8891	$101.89	$101.90	$101.90
Purchase #3	$105.73	4.446%	$110.4308	$110.43	$110.45	$110.40
Purchase #4	$46.57	13.608%	$52.9072	$52.91	$52.90	$52.90
Purchase #5	$9.61	13.331%	$10.8911	$10.89	$10.90	$10.90
Purchase #6	$54.51	8.639%	$59.2191	$59.22	$59.20	$59.20
Purchase #7	$175.34	13.136%	$198.3727	$198.37	$198.35	$198.40
7 purchase totals =	$668.42		$732.3864	$732.39	$732.40	$732.40