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	$161.55	5.813%	$170.9409	$170.94	$170.95	$170.90
Purchase #2	$128.42	6.546%	$136.8264	$136.83	$136.85	$136.80
Purchase #3	$39.52	4.864%	$41.4423	$41.44	$41.45	$41.40
Purchase #4	$70.88	10.752%	$78.501	$78.50	$78.50	$78.50
Purchase #5	$92.74	11.553%	$103.4543	$103.45	$103.45	$103.50
Purchase #6	$99.95	11.516%	$111.4602	$111.46	$111.45	$111.50
Purchase #7	$11.26	11.247%	$12.5264	$12.53	$12.55	$12.50
7 purchase totals =	$604.32		$655.1515	$655.15	$655.20	$655.10