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	$219.46	6.560%	$233.8566	$233.86	$233.85	$233.90
Purchase #2	$205.48	10.832%	$227.7376	$227.74	$227.75	$227.70
Purchase #3	$111.50	10.868%	$123.6178	$123.62	$123.60	$123.60
Purchase #4	$116.27	12.498%	$130.8014	$130.80	$130.80	$130.80
Purchase #5	$35.34	12.544%	$39.773	$39.77	$39.75	$39.80
Purchase #6	$104.65	8.497%	$113.5421	$113.54	$113.55	$113.50
Purchase #7	$168.49	6.521%	$179.4772	$179.48	$179.50	$179.50
7 purchase totals =	$961.19		$1,048.8057	$1,048.81	$1,048.80	$1,048.80