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	$176.81	7.719%	$190.458	$190.46	$190.45	$190.50
Purchase #2	$200.37	10.592%	$221.5932	$221.59	$221.60	$221.60
Purchase #3	$172.97	6.347%	$183.9484	$183.95	$183.95	$183.90
Purchase #4	$18.52	4.301%	$19.3165	$19.32	$19.30	$19.30
Purchase #5	$225.37	6.482%	$239.9785	$239.98	$240.00	$240.00
Purchase #6	$30.92	5.250%	$32.5433	$32.54	$32.55	$32.50
Purchase #7	$188.94	12.368%	$212.3081	$212.31	$212.30	$212.30
7 purchase totals =	$1,013.90		$1,100.1460	$1,100.15	$1,100.15	$1,100.10