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	$179.64	11.837%	$200.904	$200.90	$200.90	$200.90
Purchase #2	$118.96	5.758%	$125.8097	$125.81	$125.80	$125.80
Purchase #3	$213.98	11.579%	$238.7567	$238.76	$238.75	$238.80
Purchase #4	$178.93	13.705%	$203.4524	$203.45	$203.45	$203.50
Purchase #5	$239.79	11.129%	$266.4762	$266.48	$266.50	$266.50
Purchase #6	$116.59	12.617%	$131.3002	$131.30	$131.30	$131.30
Purchase #7	$250.68	10.453%	$276.8836	$276.88	$276.90	$276.90
7 purchase totals =	$1,298.57		$1,443.5828	$1,443.58	$1,443.60	$1,443.70