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	$216.91	10.769%	$240.269	$240.27	$240.25	$240.30
Purchase #2	$190.49	7.295%	$204.3862	$204.39	$204.40	$204.40
Purchase #3	$84.26	5.797%	$89.1446	$89.14	$89.15	$89.10
Purchase #4	$215.75	9.730%	$236.7425	$236.74	$236.75	$236.70
Purchase #5	$116.49	9.228%	$127.2397	$127.24	$127.25	$127.20
Purchase #6	$26.40	10.678%	$29.219	$29.22	$29.20	$29.20
Purchase #7	$142.66	11.161%	$158.5823	$158.58	$158.60	$158.60
7 purchase totals =	$992.96		$1,085.5833	$1,085.58	$1,085.60	$1,085.50