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	$56.96	9.160%	$62.1775	$62.18	$62.20	$62.20
Purchase #2	$249.69	6.650%	$266.2944	$266.29	$266.30	$266.30
Purchase #3	$179.27	11.777%	$200.3826	$200.38	$200.40	$200.40
Purchase #4	$134.25	5.821%	$142.0647	$142.06	$142.05	$142.10
Purchase #5	$96.62	5.691%	$102.1186	$102.12	$102.10	$102.10
Purchase #6	$221.28	3.601%	$229.2483	$229.25	$229.25	$229.20
Purchase #7	$48.88	7.570%	$52.5802	$52.58	$52.60	$52.60
7 purchase totals =	$986.95		$1,054.8663	$1,054.86	$1,054.90	$1,054.90