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	$79.62	3.756%	$82.6105	$82.61	$82.60	$82.60
Purchase #2	$124.56	13.492%	$141.3656	$141.37	$141.35	$141.40
Purchase #3	$10.46	3.717%	$10.8488	$10.85	$10.85	$10.80
Purchase #4	$12.59	4.611%	$13.1705	$13.17	$13.15	$13.20
Purchase #5	$153.86	8.173%	$166.435	$166.44	$166.45	$166.40
Purchase #6	$18.99	8.398%	$20.5848	$20.58	$20.60	$20.60
Purchase #7	$239.34	4.157%	$249.2894	$249.29	$249.30	$249.30
7 purchase totals =	$639.42		$684.3046	$684.31	$684.30	$684.30