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	$132.45	3.548%	$137.1493	$137.15	$137.15	$137.10
Purchase #2	$109.81	12.814%	$123.8811	$123.88	$123.90	$123.90
Purchase #3	$202.95	6.745%	$216.639	$216.64	$216.65	$216.60
Purchase #4	$59.92	6.174%	$63.6195	$63.62	$63.60	$63.60
Purchase #5	$78.46	9.243%	$85.7121	$85.71	$85.70	$85.70
Purchase #6	$102.68	6.731%	$109.5914	$109.59	$109.60	$109.60
Purchase #7	$96.28	13.671%	$109.4424	$109.44	$109.45	$109.40
7 purchase totals =	$782.55		$846.0348	$846.03	$846.05	$845.90