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	$149.95	5.462%	$158.1403	$158.14	$158.15	$158.10
Purchase #2	$112.91	3.201%	$116.5242	$116.52	$116.50	$116.50
Purchase #3	$234.53	8.542%	$254.5636	$254.56	$254.55	$254.60
Purchase #4	$32.80	13.765%	$37.3149	$37.31	$37.30	$37.30
Purchase #5	$174.28	12.868%	$196.7064	$196.71	$196.70	$196.70
Purchase #6	$8.76	3.410%	$9.0587	$9.06	$9.05	$9.10
Purchase #7	$50.37	9.433%	$55.1214	$55.12	$55.10	$55.10
7 purchase totals =	$763.60		$827.4295	$827.42	$827.35	$827.40