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	$142.78	13.617%	$162.2224	$162.22	$162.20	$162.20
Purchase #2	$170.63	12.336%	$191.6789	$191.68	$191.70	$191.70
Purchase #3	$53.29	10.265%	$58.7602	$58.76	$58.75	$58.80
Purchase #4	$85.71	4.558%	$89.6167	$89.62	$89.60	$89.60
Purchase #5	$13.35	11.837%	$14.9302	$14.93	$14.95	$14.90
Purchase #6	$24.50	3.364%	$25.3242	$25.32	$25.30	$25.30
Purchase #7	$172.34	4.193%	$179.5662	$179.57	$179.55	$179.60
7 purchase totals =	$662.60		$722.0988	$722.10	$722.05	$722.10