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	$13.39	11.180%	$14.887	$14.89	$14.90	$14.90
Purchase #2	$183.77	6.192%	$195.149	$195.15	$195.15	$195.10
Purchase #3	$167.49	8.103%	$181.0617	$181.06	$181.05	$181.10
Purchase #4	$150.97	5.263%	$158.9156	$158.92	$158.90	$158.90
Purchase #5	$197.39	12.626%	$222.3125	$222.31	$222.30	$222.30
Purchase #6	$73.32	4.409%	$76.5527	$76.55	$76.55	$76.60
Purchase #7	$149.94	12.324%	$168.4186	$168.42	$168.40	$168.40
7 purchase totals =	$936.27		$1,017.2971	$1,017.30	$1,017.25	$1,017.30