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	$79.97	3.354%	$82.6522	$82.65	$82.65	$82.70
Purchase #2	$50.42	11.256%	$56.0953	$56.10	$56.10	$56.10
Purchase #3	$48.35	11.195%	$53.7628	$53.76	$53.75	$53.80
Purchase #4	$18.61	9.229%	$20.3275	$20.33	$20.35	$20.30
Purchase #5	$47.32	10.855%	$52.4566	$52.46	$52.45	$52.50
Purchase #6	$49.31	7.310%	$52.9146	$52.91	$52.90	$52.90
Purchase #7	$113.47	9.452%	$124.1952	$124.20	$124.20	$124.20
7 purchase totals =	$407.45		$442.4042	$442.41	$442.40	$442.50