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	$222.25	8.656%	$241.488	$241.49	$241.50	$241.50
Purchase #2	$110.44	4.832%	$115.7765	$115.78	$115.80	$115.80
Purchase #3	$69.78	12.522%	$78.5179	$78.52	$78.50	$78.50
Purchase #4	$91.36	8.497%	$99.1229	$99.12	$99.10	$99.10
Purchase #5	$185.99	9.422%	$203.514	$203.51	$203.50	$203.50
Purchase #6	$175.68	5.575%	$185.4742	$185.47	$185.45	$185.50
Purchase #7	$114.75	13.438%	$130.1701	$130.17	$130.15	$130.20
7 purchase totals =	$970.25		$1,054.0636	$1,054.06	$1,054.00	$1,054.10