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	$148.65	9.319%	$162.5027	$162.50	$162.50	$162.50
Purchase #2	$174.71	9.647%	$191.5643	$191.56	$191.55	$191.60
Purchase #3	$116.27	9.827%	$127.6959	$127.70	$127.70	$127.70
Purchase #4	$102.85	13.791%	$117.034	$117.03	$117.05	$117.00
Purchase #5	$120.95	11.223%	$134.5242	$134.52	$134.50	$134.50
Purchase #6	$17.58	13.228%	$19.9055	$19.91	$19.90	$19.90
Purchase #7	$12.32	7.607%	$13.2572	$13.26	$13.25	$13.30
7 purchase totals =	$693.33		$766.4838	$766.48	$766.45	$766.50