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	$181.43	13.332%	$205.6182	$205.62	$205.60	$205.60
Purchase #2	$161.68	9.644%	$177.2724	$177.27	$177.25	$177.30
Purchase #3	$80.86	12.615%	$91.0605	$91.06	$91.05	$91.10
Purchase #4	$38.90	13.461%	$44.1363	$44.14	$44.15	$44.10
Purchase #5	$134.53	5.802%	$142.3354	$142.34	$142.35	$142.30
Purchase #6	$116.60	9.271%	$127.41	$127.41	$127.40	$127.40
Purchase #7	$78.73	4.457%	$82.239	$82.24	$82.25	$82.20
7 purchase totals =	$792.73		$870.0718	$870.08	$870.05	$870.00