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	$219.67	10.291%	$242.2762	$242.28	$242.30	$242.30
Purchase #2	$98.25	7.532%	$105.6502	$105.65	$105.65	$105.70
Purchase #3	$199.40	11.789%	$222.9073	$222.91	$222.90	$222.90
Purchase #4	$102.37	10.270%	$112.8834	$112.88	$112.90	$112.90
Purchase #5	$143.79	3.405%	$148.686	$148.69	$148.70	$148.70
Purchase #6	$66.40	6.313%	$70.5918	$70.59	$70.60	$70.60
Purchase #7	$171.37	5.623%	$181.0061	$181.01	$181.00	$181.00
7 purchase totals =	$1,001.25		$1,084.0010	$1,084.01	$1,084.05	$1,084.10