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	$134.47	7.404%	$144.4262	$144.43	$144.45	$144.40
Purchase #2	$114.64	10.373%	$126.5316	$126.53	$126.55	$126.50
Purchase #3	$217.37	10.488%	$240.1678	$240.17	$240.15	$240.20
Purchase #4	$77.62	9.857%	$85.271	$85.27	$85.25	$85.30
Purchase #5	$61.72	4.275%	$64.3585	$64.36	$64.35	$64.40
Purchase #6	$33.88	13.681%	$38.5151	$38.52	$38.50	$38.50
Purchase #7	$148.70	7.805%	$160.306	$160.31	$160.30	$160.30
7 purchase totals =	$788.40		$859.5762	$859.59	$859.55	$859.60