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	$56.57	4.666%	$59.2096	$59.21	$59.20	$59.20
Purchase #2	$166.98	3.225%	$172.3651	$172.37	$172.35	$172.40
Purchase #3	$15.25	6.425%	$16.2298	$16.23	$16.25	$16.20
Purchase #4	$40.75	8.404%	$44.1746	$44.17	$44.15	$44.20
Purchase #5	$90.86	9.694%	$99.668	$99.67	$99.65	$99.70
Purchase #6	$238.31	11.866%	$266.5879	$266.59	$266.60	$266.60
Purchase #7	$16.64	8.413%	$18.0399	$18.04	$18.05	$18.00
7 purchase totals =	$625.36		$676.2749	$676.28	$676.25	$676.30