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	$111.43	4.673%	$116.6371	$116.64	$116.65	$116.60
Purchase #2	$170.62	7.673%	$183.7117	$183.71	$183.70	$183.70
Purchase #3	$207.39	9.258%	$226.5902	$226.59	$226.60	$226.60
Purchase #4	$49.32	12.585%	$55.5269	$55.53	$55.55	$55.50
Purchase #5	$30.52	9.629%	$33.4588	$33.46	$33.45	$33.50
Purchase #6	$96.72	3.627%	$100.228	$100.23	$100.25	$100.20
Purchase #7	$240.74	7.611%	$259.0627	$259.06	$259.05	$259.10
7 purchase totals =	$906.74		$975.2154	$975.22	$975.25	$975.20