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	$166.97	8.578%	$181.2927	$181.29	$181.30	$181.30
Purchase #2	$171.76	6.225%	$182.4521	$182.45	$182.45	$182.50
Purchase #3	$5.78	10.340%	$6.3777	$6.38	$6.40	$6.40
Purchase #4	$29.80	10.850%	$33.0333	$33.03	$33.05	$33.00
Purchase #5	$171.88	8.106%	$185.8126	$185.81	$185.80	$185.80
Purchase #6	$153.57	5.781%	$162.4479	$162.45	$162.45	$162.40
Purchase #7	$176.99	4.826%	$185.5315	$185.53	$185.55	$185.50
7 purchase totals =	$876.75		$936.9478	$936.94	$937.00	$936.90