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	$79.98	6.836%	$85.4474	$85.45	$85.45	$85.40
Purchase #2	$184.28	11.526%	$205.5201	$205.52	$205.50	$205.50
Purchase #3	$173.88	11.226%	$193.3998	$193.40	$193.40	$193.40
Purchase #4	$195.68	7.529%	$210.4127	$210.41	$210.40	$210.40
Purchase #5	$89.25	12.124%	$100.0707	$100.07	$100.05	$100.10
Purchase #6	$190.94	3.698%	$198.001	$198.00	$198.00	$198.00
Purchase #7	$83.26	8.196%	$90.084	$90.08	$90.10	$90.10
7 purchase totals =	$997.27		$1,082.9357	$1,082.93	$1,082.90	$1,082.90