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	$162.89	11.212%	$181.1532	$181.15	$181.15	$181.20
Purchase #2	$49.93	8.275%	$54.0617	$54.06	$54.05	$54.10
Purchase #3	$71.54	12.425%	$80.4288	$80.43	$80.45	$80.40
Purchase #4	$117.65	6.431%	$125.2161	$125.22	$125.20	$125.20
Purchase #5	$51.86	5.140%	$54.5256	$54.53	$54.55	$54.50
Purchase #6	$39.78	12.624%	$44.8018	$44.80	$44.80	$44.80
Purchase #7	$39.74	4.860%	$41.6714	$41.67	$41.65	$41.70
7 purchase totals =	$533.39		$581.8586	$581.86	$581.85	$581.90