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	$221.45	9.694%	$242.9174	$242.92	$242.90	$242.90
Purchase #2	$238.48	6.145%	$253.1346	$253.13	$253.15	$253.10
Purchase #3	$62.76	5.192%	$66.0185	$66.02	$66.00	$66.00
Purchase #4	$42.66	8.190%	$46.1539	$46.15	$46.15	$46.20
Purchase #5	$180.48	6.549%	$192.2996	$192.30	$192.30	$192.30
Purchase #6	$144.37	4.778%	$151.268	$151.27	$151.25	$151.30
Purchase #7	$85.46	12.485%	$96.1297	$96.13	$96.15	$96.10
7 purchase totals =	$975.66		$1,047.9217	$1,047.92	$1,047.90	$1,047.90