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	$21.42	4.836%	$22.4559	$22.46	$22.45	$22.50
Purchase #2	$103.72	7.263%	$111.2532	$111.25	$111.25	$111.30
Purchase #3	$180.52	10.109%	$198.7688	$198.77	$198.75	$198.80
Purchase #4	$135.50	9.432%	$148.2804	$148.28	$148.30	$148.30
Purchase #5	$229.36	11.141%	$254.913	$254.91	$254.90	$254.90
Purchase #6	$187.87	4.358%	$196.0574	$196.06	$196.05	$196.10
Purchase #7	$52.84	7.451%	$56.7771	$56.78	$56.80	$56.80
7 purchase totals =	$911.23		$988.5058	$988.51	$988.50	$988.70