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	$227.52	4.846%	$238.5456	$238.55	$238.55	$238.50
Purchase #2	$197.98	11.337%	$220.425	$220.43	$220.45	$220.40
Purchase #3	$11.37	11.612%	$12.6903	$12.69	$12.70	$12.70
Purchase #4	$132.83	4.660%	$139.0199	$139.02	$139.00	$139.00
Purchase #5	$241.39	9.371%	$264.0107	$264.01	$264.00	$264.00
Purchase #6	$65.96	9.692%	$72.3528	$72.35	$72.35	$72.40
Purchase #7	$98.37	12.852%	$111.0125	$111.01	$111.00	$111.00
7 purchase totals =	$975.42		$1,058.0568	$1,058.06	$1,058.05	$1,058.00