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	$52.84	3.381%	$54.6265	$54.63	$54.65	$54.60
Purchase #2	$84.74	5.639%	$89.5185	$89.52	$89.50	$89.50
Purchase #3	$111.75	11.771%	$124.9041	$124.90	$124.90	$124.90
Purchase #4	$237.32	3.583%	$245.8232	$245.82	$245.80	$245.80
Purchase #5	$117.42	9.121%	$128.1299	$128.13	$128.15	$128.10
Purchase #6	$229.55	13.288%	$260.0526	$260.05	$260.05	$260.10
Purchase #7	$152.58	5.106%	$160.3707	$160.37	$160.35	$160.40
7 purchase totals =	$986.20		$1,063.4255	$1,063.42	$1,063.40	$1,063.40