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	$97.62	8.529%	$105.946	$105.95	$105.95	$105.90
Purchase #2	$151.39	3.537%	$156.7447	$156.74	$156.75	$156.70
Purchase #3	$218.56	13.595%	$248.2732	$248.27	$248.25	$248.30
Purchase #4	$212.99	5.864%	$225.4797	$225.48	$225.50	$225.50
Purchase #5	$79.82	11.840%	$89.2707	$89.27	$89.25	$89.30
Purchase #6	$109.67	10.466%	$121.1481	$121.15	$121.15	$121.10
Purchase #7	$9.60	4.695%	$10.0507	$10.05	$10.05	$10.10
7 purchase totals =	$879.65		$956.9131	$956.91	$956.90	$956.90