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	$244.92	13.172%	$277.1809	$277.18	$277.20	$277.20
Purchase #2	$37.27	10.198%	$41.0708	$41.07	$41.05	$41.10
Purchase #3	$217.74	3.710%	$225.8182	$225.82	$225.80	$225.80
Purchase #4	$39.76	10.225%	$43.8255	$43.83	$43.85	$43.80
Purchase #5	$122.98	6.445%	$130.9061	$130.91	$130.90	$130.90
Purchase #6	$184.92	12.617%	$208.2514	$208.25	$208.25	$208.30
Purchase #7	$150.96	13.522%	$171.3728	$171.37	$171.35	$171.40
7 purchase totals =	$998.55		$1,098.4257	$1,098.43	$1,098.40	$1,098.50