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	$67.76	6.701%	$72.3006	$72.30	$72.30	$72.30
Purchase #2	$249.91	6.461%	$266.0567	$266.06	$266.05	$266.10
Purchase #3	$89.76	7.193%	$96.2164	$96.22	$96.20	$96.20
Purchase #4	$40.88	11.520%	$45.5894	$45.59	$45.60	$45.60
Purchase #5	$240.90	6.265%	$255.9924	$255.99	$256.00	$256.00
Purchase #6	$132.58	6.422%	$141.0943	$141.09	$141.10	$141.10
Purchase #7	$162.50	11.568%	$181.298	$181.30	$181.30	$181.30
7 purchase totals =	$984.29		$1,058.5478	$1,058.55	$1,058.55	$1,058.60