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	$116.25	9.415%	$127.1949	$127.19	$127.20	$127.20
Purchase #2	$197.67	3.339%	$204.2702	$204.27	$204.25	$204.30
Purchase #3	$125.28	12.224%	$140.5942	$140.59	$140.60	$140.60
Purchase #4	$36.41	6.591%	$38.8098	$38.81	$38.80	$38.80
Purchase #5	$81.27	13.714%	$92.4154	$92.42	$92.40	$92.40
Purchase #6	$227.74	13.406%	$258.2708	$258.27	$258.25	$258.30
Purchase #7	$80.39	10.781%	$89.0568	$89.06	$89.05	$89.10
7 purchase totals =	$865.01		$950.6121	$950.61	$950.55	$950.70