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	$53.48	11.788%	$59.7842	$59.78	$59.80	$59.80
Purchase #2	$124.46	3.202%	$128.4452	$128.45	$128.45	$128.40
Purchase #3	$96.90	8.495%	$105.1317	$105.13	$105.15	$105.10
Purchase #4	$132.38	12.601%	$149.0612	$149.06	$149.05	$149.10
Purchase #5	$47.54	12.180%	$53.3304	$53.33	$53.35	$53.30
Purchase #6	$53.69	8.724%	$58.3739	$58.37	$58.35	$58.40
Purchase #7	$160.90	13.298%	$182.2965	$182.30	$182.30	$182.30
7 purchase totals =	$669.35		$736.4231	$736.42	$736.45	$736.40