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	$99.71	11.844%	$111.5197	$111.52	$111.50	$111.50
Purchase #2	$178.89	7.215%	$191.7969	$191.80	$191.80	$191.80
Purchase #3	$144.59	4.718%	$151.4118	$151.41	$151.40	$151.40
Purchase #4	$112.54	8.129%	$121.6884	$121.69	$121.70	$121.70
Purchase #5	$91.25	3.646%	$94.577	$94.58	$94.60	$94.60
Purchase #6	$79.38	11.358%	$88.396	$88.40	$88.40	$88.40
Purchase #7	$44.88	5.806%	$47.4857	$47.49	$47.50	$47.50
7 purchase totals =	$751.24		$806.8755	$806.89	$806.90	$806.90