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	$52.58	3.238%	$54.2825	$54.28	$54.30	$54.30
Purchase #2	$77.98	4.606%	$81.5718	$81.57	$81.55	$81.60
Purchase #3	$233.97	13.751%	$266.1432	$266.14	$266.15	$266.10
Purchase #4	$59.74	13.133%	$67.5857	$67.59	$67.60	$67.60
Purchase #5	$94.95	6.721%	$101.3316	$101.33	$101.35	$101.30
Purchase #6	$51.93	4.546%	$54.2907	$54.29	$54.30	$54.30
Purchase #7	$57.33	9.471%	$62.7597	$62.76	$62.75	$62.80
7 purchase totals =	$628.48		$687.9652	$687.96	$688.00	$688.00