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	$183.78	10.107%	$202.3546	$202.35	$202.35	$202.40
Purchase #2	$19.69	5.749%	$20.822	$20.82	$20.80	$20.80
Purchase #3	$61.93	5.836%	$65.5442	$65.54	$65.55	$65.50
Purchase #4	$230.73	6.501%	$245.7298	$245.73	$245.75	$245.70
Purchase #5	$116.66	10.103%	$128.4462	$128.45	$128.45	$128.40
Purchase #6	$183.60	6.870%	$196.2133	$196.21	$196.20	$196.20
Purchase #7	$134.80	5.328%	$141.9821	$141.98	$142.00	$142.00
7 purchase totals =	$931.19		$1,001.0922	$1,001.08	$1,001.10	$1,001.00