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	$108.33	5.782%	$114.5936	$114.59	$114.60	$114.60
Purchase #2	$40.95	5.378%	$43.1523	$43.15	$43.15	$43.20
Purchase #3	$135.44	6.716%	$144.5362	$144.54	$144.55	$144.50
Purchase #4	$150.42	10.214%	$165.7839	$165.78	$165.80	$165.80
Purchase #5	$233.64	12.712%	$263.3403	$263.34	$263.35	$263.30
Purchase #6	$146.39	3.752%	$151.8826	$151.88	$151.90	$151.90
Purchase #7	$196.55	9.371%	$214.9687	$214.97	$214.95	$215.00
7 purchase totals =	$1,011.72		$1,098.2576	$1,098.25	$1,098.30	$1,098.30