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	$209.82	9.869%	$230.5271	$230.53	$230.55	$230.50
Purchase #2	$112.64	13.469%	$127.8115	$127.81	$127.80	$127.80
Purchase #3	$36.59	12.859%	$41.2951	$41.30	$41.30	$41.30
Purchase #4	$41.41	10.381%	$45.7088	$45.71	$45.70	$45.70
Purchase #5	$151.49	8.493%	$164.356	$164.36	$164.35	$164.40
Purchase #6	$133.62	13.739%	$151.9781	$151.98	$152.00	$152.00
Purchase #7	$238.82	10.426%	$263.7194	$263.72	$263.70	$263.70
7 purchase totals =	$924.39		$1,025.3960	$1,025.41	$1,025.40	$1,025.40