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	$246.55	6.629%	$262.8938	$262.89	$262.90	$262.90
Purchase #2	$176.81	4.818%	$185.3287	$185.33	$185.35	$185.30
Purchase #3	$197.61	11.539%	$220.4122	$220.41	$220.40	$220.40
Purchase #4	$142.85	10.661%	$158.0792	$158.08	$158.10	$158.10
Purchase #5	$150.47	6.317%	$159.9752	$159.98	$160.00	$160.00
Purchase #6	$167.60	3.655%	$173.7258	$173.73	$173.75	$173.70
Purchase #7	$221.78	8.508%	$240.649	$240.65	$240.65	$240.60
7 purchase totals =	$1,303.67		$1,401.0639	$1,401.07	$1,401.15	$1,401.00