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	$132.30	3.834%	$137.3724	$137.37	$137.35	$137.40
Purchase #2	$226.54	10.564%	$250.4717	$250.47	$250.45	$250.50
Purchase #3	$186.53	4.254%	$194.465	$194.47	$194.45	$194.50
Purchase #4	$218.40	11.751%	$244.0642	$244.06	$244.05	$244.10
Purchase #5	$233.97	9.681%	$256.6206	$256.62	$256.60	$256.60
Purchase #6	$59.75	13.200%	$67.637	$67.64	$67.65	$67.60
Purchase #7	$30.40	6.777%	$32.4602	$32.46	$32.45	$32.50
7 purchase totals =	$1,087.89		$1,183.0911	$1,183.09	$1,183.00	$1,183.20