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	$100.76	4.573%	$105.3678	$105.37	$105.35	$105.40
Purchase #2	$183.62	9.366%	$200.8178	$200.82	$200.80	$200.80
Purchase #3	$231.47	4.817%	$242.6199	$242.62	$242.60	$242.60
Purchase #4	$177.46	3.645%	$183.9284	$183.93	$183.95	$183.90
Purchase #5	$134.82	3.198%	$139.1315	$139.13	$139.15	$139.10
Purchase #6	$95.52	10.533%	$105.5811	$105.58	$105.60	$105.60
Purchase #7	$196.32	12.334%	$220.5341	$220.53	$220.55	$220.50
7 purchase totals =	$1,119.97		$1,197.9806	$1,197.98	$1,198.00	$1,197.90