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	$130.43	9.493%	$142.8117	$142.81	$142.80	$142.80
Purchase #2	$31.72	6.705%	$33.8468	$33.85	$33.85	$33.80
Purchase #3	$10.41	3.775%	$10.803	$10.80	$10.80	$10.80
Purchase #4	$247.70	4.722%	$259.3964	$259.40	$259.40	$259.40
Purchase #5	$235.90	3.499%	$244.1541	$244.15	$244.15	$244.20
Purchase #6	$231.35	10.798%	$256.3312	$256.33	$256.35	$256.30
Purchase #7	$126.74	13.340%	$143.6471	$143.65	$143.65	$143.60
7 purchase totals =	$1,014.25		$1,090.9903	$1,090.99	$1,091.00	$1,090.90