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	$56.32	5.464%	$59.3973	$59.40	$59.40	$59.40
Purchase #2	$241.27	5.605%	$254.7932	$254.79	$254.80	$254.80
Purchase #3	$187.60	9.643%	$205.6903	$205.69	$205.70	$205.70
Purchase #4	$171.84	6.618%	$183.2124	$183.21	$183.20	$183.20
Purchase #5	$57.95	13.228%	$65.6156	$65.62	$65.60	$65.60
Purchase #6	$121.80	7.755%	$131.2456	$131.25	$131.25	$131.20
Purchase #7	$98.92	10.545%	$109.3511	$109.35	$109.35	$109.40
7 purchase totals =	$935.70		$1,009.3055	$1,009.31	$1,009.30	$1,009.30