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	$136.64	3.459%	$141.3664	$141.37	$141.35	$141.40
Purchase #2	$47.75	13.712%	$54.2975	$54.30	$54.30	$54.30
Purchase #3	$149.77	13.243%	$169.604	$169.60	$169.60	$169.60
Purchase #4	$67.53	10.176%	$74.4019	$74.40	$74.40	$74.40
Purchase #5	$156.41	9.716%	$171.6068	$171.61	$171.60	$171.60
Purchase #6	$65.94	10.298%	$72.7305	$72.73	$72.75	$72.70
Purchase #7	$121.33	5.537%	$128.048	$128.05	$128.05	$128.00
7 purchase totals =	$745.37		$812.0551	$812.06	$812.05	$812.00