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	$41.27	3.261%	$42.6158	$42.62	$42.60	$42.60
Purchase #2	$187.86	10.387%	$207.373	$207.37	$207.35	$207.40
Purchase #3	$62.70	4.109%	$65.2763	$65.28	$65.30	$65.30
Purchase #4	$19.46	13.511%	$22.0892	$22.09	$22.10	$22.10
Purchase #5	$40.30	13.846%	$45.8799	$45.88	$45.90	$45.90
Purchase #6	$162.64	10.366%	$179.4993	$179.50	$179.50	$179.50
Purchase #7	$207.73	12.678%	$234.066	$234.07	$234.05	$234.10
7 purchase totals =	$721.96		$796.7995	$796.81	$796.80	$796.90