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	$135.72	13.562%	$154.1263	$154.13	$154.15	$154.10
Purchase #2	$82.26	6.483%	$87.5929	$87.59	$87.60	$87.60
Purchase #3	$226.60	7.611%	$243.8465	$243.85	$243.85	$243.80
Purchase #4	$240.79	6.234%	$255.8008	$255.80	$255.80	$255.80
Purchase #5	$59.78	4.175%	$62.2758	$62.28	$62.30	$62.30
Purchase #6	$91.95	10.683%	$101.773	$101.77	$101.75	$101.80
Purchase #7	$146.61	10.720%	$162.3266	$162.33	$162.35	$162.30
7 purchase totals =	$983.71		$1,067.7419	$1,067.75	$1,067.80	$1,067.70