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	$139.81	13.705%	$158.971	$158.97	$158.95	$159.00
Purchase #2	$112.94	3.436%	$116.8206	$116.82	$116.80	$116.80
Purchase #3	$10.53	3.435%	$10.8917	$10.89	$10.90	$10.90
Purchase #4	$172.56	6.382%	$183.5728	$183.57	$183.55	$183.60
Purchase #5	$71.76	10.493%	$79.2898	$79.29	$79.30	$79.30
Purchase #6	$241.45	11.391%	$268.9536	$268.95	$268.95	$269.00
Purchase #7	$195.76	7.198%	$209.8508	$209.85	$209.85	$209.90
7 purchase totals =	$944.81		$1,028.3503	$1,028.34	$1,028.30	$1,028.50