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	$228.40	5.635%	$241.2703	$241.27	$241.25	$241.30
Purchase #2	$133.92	13.362%	$151.8144	$151.81	$151.80	$151.80
Purchase #3	$244.36	3.680%	$253.3524	$253.35	$253.35	$253.40
Purchase #4	$84.91	6.156%	$90.1371	$90.14	$90.15	$90.10
Purchase #5	$112.94	4.197%	$117.6801	$117.68	$117.70	$117.70
Purchase #6	$62.76	5.474%	$66.1955	$66.20	$66.20	$66.20
Purchase #7	$150.35	3.675%	$155.8754	$155.88	$155.90	$155.90
7 purchase totals =	$1,017.64		$1,076.3252	$1,076.33	$1,076.35	$1,076.40