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	$246.82	5.804%	$261.1454	$261.15	$261.15	$261.10
Purchase #2	$150.75	7.326%	$161.7939	$161.79	$161.80	$161.80
Purchase #3	$222.97	6.451%	$237.3538	$237.35	$237.35	$237.40
Purchase #4	$7.75	4.607%	$8.107	$8.11	$8.10	$8.10
Purchase #5	$241.87	11.570%	$269.8544	$269.85	$269.85	$269.90
Purchase #6	$205.99	4.820%	$215.9187	$215.92	$215.90	$215.90
Purchase #7	$38.56	9.335%	$42.1596	$42.16	$42.15	$42.20
7 purchase totals =	$1,114.71		$1,196.3328	$1,196.33	$1,196.30	$1,196.40