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	$94.49	12.663%	$106.4553	$106.46	$106.45	$106.50
Purchase #2	$127.49	4.436%	$133.1455	$133.15	$133.15	$133.10
Purchase #3	$47.61	13.296%	$53.9402	$53.94	$53.95	$53.90
Purchase #4	$96.95	9.830%	$106.4802	$106.48	$106.50	$106.50
Purchase #5	$171.46	5.141%	$180.2748	$180.27	$180.25	$180.30
Purchase #6	$160.39	7.532%	$172.4706	$172.47	$172.45	$172.50
Purchase #7	$237.27	3.277%	$245.0453	$245.05	$245.05	$245.00
7 purchase totals =	$935.66		$997.8119	$997.82	$997.80	$997.80