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	$215.43	9.240%	$235.3357	$235.34	$235.35	$235.30
Purchase #2	$171.95	7.534%	$184.9047	$184.90	$184.90	$184.90
Purchase #3	$85.88	12.125%	$96.293	$96.29	$96.30	$96.30
Purchase #4	$144.84	13.269%	$164.0588	$164.06	$164.05	$164.10
Purchase #5	$33.69	12.643%	$37.9494	$37.95	$37.95	$37.90
Purchase #6	$121.98	4.230%	$127.1398	$127.14	$127.15	$127.10
Purchase #7	$54.45	3.380%	$56.2904	$56.29	$56.30	$56.30
7 purchase totals =	$828.22		$901.9718	$901.97	$902.00	$901.90