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	$50.74	6.360%	$53.9671	$53.97	$53.95	$54.00
Purchase #2	$186.91	5.212%	$196.6517	$196.65	$196.65	$196.70
Purchase #3	$163.32	12.262%	$183.3463	$183.35	$183.35	$183.30
Purchase #4	$33.42	11.110%	$37.133	$37.13	$37.15	$37.10
Purchase #5	$71.95	7.612%	$77.4268	$77.43	$77.45	$77.40
Purchase #6	$97.79	12.261%	$109.78	$109.78	$109.80	$109.80
Purchase #7	$161.63	6.792%	$172.6079	$172.61	$172.60	$172.60
7 purchase totals =	$765.76		$830.9128	$830.92	$830.95	$830.90