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	$169.95	10.221%	$187.3206	$187.32	$187.30	$187.30
Purchase #2	$109.33	6.829%	$116.7961	$116.80	$116.80	$116.80
Purchase #3	$19.96	8.194%	$21.5955	$21.60	$21.60	$21.60
Purchase #4	$59.37	4.531%	$62.0601	$62.06	$62.05	$62.10
Purchase #5	$200.62	11.370%	$223.4305	$223.43	$223.45	$223.40
Purchase #6	$142.29	4.192%	$148.2548	$148.25	$148.25	$148.30
Purchase #7	$104.32	4.671%	$109.1928	$109.19	$109.20	$109.20
7 purchase totals =	$805.84		$868.6504	$868.65	$868.65	$868.70