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	$38.64	11.385%	$43.0392	$43.04	$43.05	$43.00
Purchase #2	$39.35	7.324%	$42.232	$42.23	$42.25	$42.20
Purchase #3	$86.27	3.322%	$89.1359	$89.14	$89.15	$89.10
Purchase #4	$53.62	12.397%	$60.2673	$60.27	$60.25	$60.30
Purchase #5	$185.46	12.497%	$208.6369	$208.64	$208.65	$208.60
Purchase #6	$194.91	12.655%	$219.5759	$219.58	$219.60	$219.60
Purchase #7	$169.76	9.493%	$185.8753	$185.88	$185.90	$185.90
7 purchase totals =	$768.01		$848.7625	$848.78	$848.85	$848.70