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	$63.69	3.360%	$65.83	$65.83	$65.85	$65.80
Purchase #2	$84.51	6.741%	$90.2068	$90.21	$90.20	$90.20
Purchase #3	$167.70	13.642%	$190.5776	$190.58	$190.60	$190.60
Purchase #4	$116.44	3.739%	$120.7937	$120.79	$120.80	$120.80
Purchase #5	$50.36	13.467%	$57.142	$57.14	$57.15	$57.10
Purchase #6	$71.25	10.449%	$78.6949	$78.69	$78.70	$78.70
Purchase #7	$166.63	3.856%	$173.0553	$173.06	$173.05	$173.10
7 purchase totals =	$720.58		$776.3003	$776.30	$776.35	$776.30