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	$237.98	8.656%	$258.5795	$258.58	$258.60	$258.60
Purchase #2	$53.39	10.550%	$59.0226	$59.02	$59.00	$59.00
Purchase #3	$39.52	10.377%	$43.621	$43.62	$43.60	$43.60
Purchase #4	$89.88	11.651%	$100.3519	$100.35	$100.35	$100.40
Purchase #5	$234.83	12.775%	$264.8295	$264.83	$264.85	$264.80
Purchase #6	$205.77	3.287%	$212.5337	$212.53	$212.55	$212.50
Purchase #7	$153.31	12.611%	$172.6439	$172.64	$172.65	$172.60
7 purchase totals =	$1,014.68		$1,111.5821	$1,111.57	$1,111.60	$1,111.50