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	$79.68	7.813%	$85.9054	$85.91	$85.90	$85.90
Purchase #2	$123.54	11.275%	$137.4691	$137.47	$137.45	$137.50
Purchase #3	$71.76	7.726%	$77.3042	$77.30	$77.30	$77.30
Purchase #4	$50.59	7.535%	$54.402	$54.40	$54.40	$54.40
Purchase #5	$136.39	4.685%	$142.7799	$142.78	$142.80	$142.80
Purchase #6	$109.38	13.413%	$124.0511	$124.05	$124.05	$124.10
Purchase #7	$112.32	8.724%	$122.1188	$122.12	$122.10	$122.10
7 purchase totals =	$683.66		$744.0305	$744.03	$744.00	$744.10