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	$154.78	4.172%	$161.2374	$161.24	$161.25	$161.20
Purchase #2	$220.30	4.638%	$230.5175	$230.52	$230.50	$230.50
Purchase #3	$78.49	13.827%	$89.3428	$89.34	$89.35	$89.30
Purchase #4	$104.95	8.563%	$113.9369	$113.94	$113.95	$113.90
Purchase #5	$54.77	3.853%	$56.8803	$56.88	$56.90	$56.90
Purchase #6	$118.30	11.489%	$131.8915	$131.89	$131.90	$131.90
Purchase #7	$93.82	11.735%	$104.8298	$104.83	$104.85	$104.80
7 purchase totals =	$825.41		$888.6362	$888.64	$888.70	$888.50