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	$155.36	11.328%	$172.9592	$172.96	$172.95	$173.00
Purchase #2	$129.28	11.582%	$144.2532	$144.25	$144.25	$144.30
Purchase #3	$51.36	5.260%	$54.0615	$54.06	$54.05	$54.10
Purchase #4	$98.61	3.217%	$101.7823	$101.78	$101.80	$101.80
Purchase #5	$127.51	4.511%	$133.262	$133.26	$133.25	$133.30
Purchase #6	$103.26	10.702%	$114.3109	$114.31	$114.30	$114.30
Purchase #7	$93.99	12.542%	$105.7782	$105.78	$105.80	$105.80
7 purchase totals =	$759.37		$826.4073	$826.40	$826.40	$826.60