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	$211.69	3.707%	$219.5373	$219.54	$219.55	$219.50
Purchase #2	$84.28	11.570%	$94.0312	$94.03	$94.05	$94.00
Purchase #3	$222.71	4.666%	$233.1016	$233.10	$233.10	$233.10
Purchase #4	$136.57	12.346%	$153.4309	$153.43	$153.45	$153.40
Purchase #5	$115.38	7.464%	$123.992	$123.99	$124.00	$124.00
Purchase #6	$209.76	11.211%	$233.2762	$233.28	$233.30	$233.30
Purchase #7	$213.93	4.114%	$222.7311	$222.73	$222.75	$222.70
7 purchase totals =	$1,194.32		$1,280.1003	$1,280.10	$1,280.20	$1,280.00