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	$205.37	10.448%	$226.8271	$226.83	$226.85	$226.80
Purchase #2	$104.35	3.204%	$107.6934	$107.69	$107.70	$107.70
Purchase #3	$193.63	13.223%	$219.2337	$219.23	$219.25	$219.20
Purchase #4	$240.25	7.817%	$259.0303	$259.03	$259.05	$259.00
Purchase #5	$90.46	10.339%	$99.8127	$99.81	$99.80	$99.80
Purchase #6	$116.35	9.854%	$127.8151	$127.82	$127.80	$127.80
Purchase #7	$105.30	6.465%	$112.1076	$112.11	$112.10	$112.10
7 purchase totals =	$1,055.71		$1,152.5199	$1,152.52	$1,152.55	$1,152.40