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	$137.72	13.606%	$156.4582	$156.46	$156.45	$156.50
Purchase #2	$226.82	12.298%	$254.7143	$254.71	$254.70	$254.70
Purchase #3	$201.45	10.685%	$222.9749	$222.97	$222.95	$223.00
Purchase #4	$72.77	13.756%	$82.7802	$82.78	$82.80	$82.80
Purchase #5	$106.55	6.164%	$113.1177	$113.12	$113.10	$113.10
Purchase #6	$150.91	5.114%	$158.6275	$158.63	$158.65	$158.60
Purchase #7	$173.42	5.182%	$182.4066	$182.41	$182.40	$182.40
7 purchase totals =	$1,069.64		$1,171.0794	$1,171.08	$1,171.05	$1,171.10