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	$52.64	3.244%	$54.3476	$54.35	$54.35	$54.30
Purchase #2	$156.35	10.181%	$172.268	$172.27	$172.25	$172.30
Purchase #3	$142.98	13.661%	$162.5125	$162.51	$162.50	$162.50
Purchase #4	$72.40	11.130%	$80.4581	$80.46	$80.45	$80.50
Purchase #5	$230.61	3.299%	$238.2178	$238.22	$238.20	$238.20
Purchase #6	$136.65	8.617%	$148.4251	$148.43	$148.45	$148.40
Purchase #7	$84.73	4.186%	$88.2768	$88.28	$88.30	$88.30
7 purchase totals =	$876.36		$944.5059	$944.52	$944.50	$944.50