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	$224.57	3.445%	$232.3064	$232.31	$232.30	$232.30
Purchase #2	$173.63	13.131%	$196.4294	$196.43	$196.45	$196.40
Purchase #3	$89.90	8.214%	$97.2844	$97.28	$97.30	$97.30
Purchase #4	$57.64	10.722%	$63.8202	$63.82	$63.80	$63.80
Purchase #5	$136.95	8.502%	$148.5935	$148.59	$148.60	$148.60
Purchase #6	$92.72	11.750%	$103.6146	$103.61	$103.60	$103.60
Purchase #7	$138.55	9.433%	$151.6194	$151.62	$151.60	$151.60
7 purchase totals =	$913.96		$993.6679	$993.66	$993.65	$993.60