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	$202.48	9.870%	$222.4648	$222.46	$222.45	$222.50
Purchase #2	$144.54	6.583%	$154.0551	$154.06	$154.05	$154.10
Purchase #3	$197.35	7.244%	$211.646	$211.65	$211.65	$211.60
Purchase #4	$105.77	4.590%	$110.6248	$110.62	$110.60	$110.60
Purchase #5	$33.49	12.349%	$37.6257	$37.63	$37.65	$37.60
Purchase #6	$111.65	13.751%	$127.003	$127.00	$127.00	$127.00
Purchase #7	$179.45	13.351%	$203.4084	$203.41	$203.40	$203.40
7 purchase totals =	$974.73		$1,066.8278	$1,066.83	$1,066.80	$1,066.80