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	$229.78	3.615%	$238.0865	$238.09	$238.10	$238.10
Purchase #2	$87.81	9.789%	$96.4057	$96.41	$96.40	$96.40
Purchase #3	$81.38	10.478%	$89.907	$89.91	$89.90	$89.90
Purchase #4	$246.42	6.790%	$263.1519	$263.15	$263.15	$263.20
Purchase #5	$139.86	13.260%	$158.4054	$158.41	$158.40	$158.40
Purchase #6	$214.77	5.724%	$227.0634	$227.06	$227.05	$227.10
Purchase #7	$92.92	7.639%	$100.0182	$100.02	$100.00	$100.00
7 purchase totals =	$1,092.94		$1,173.0381	$1,173.05	$1,173.00	$1,173.10