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	$78.83	9.432%	$86.2652	$86.27	$86.25	$86.30
Purchase #2	$44.82	10.512%	$49.5315	$49.53	$49.55	$49.50
Purchase #3	$44.39	4.596%	$46.4302	$46.43	$46.45	$46.40
Purchase #4	$219.53	3.433%	$227.0665	$227.07	$227.05	$227.10
Purchase #5	$202.68	6.340%	$215.5299	$215.53	$215.55	$215.50
Purchase #6	$94.57	11.167%	$105.1306	$105.13	$105.15	$105.10
Purchase #7	$139.77	11.657%	$156.063	$156.06	$156.05	$156.10
7 purchase totals =	$824.59		$886.0169	$886.02	$886.05	$886.00