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	$68.82	10.558%	$76.086	$76.09	$76.10	$76.10
Purchase #2	$212.69	12.711%	$239.725	$239.73	$239.75	$239.70
Purchase #3	$154.39	3.653%	$160.0299	$160.03	$160.05	$160.00
Purchase #4	$36.88	7.171%	$39.5247	$39.52	$39.50	$39.50
Purchase #5	$223.91	4.127%	$233.1508	$233.15	$233.15	$233.20
Purchase #6	$12.47	12.805%	$14.0668	$14.07	$14.05	$14.10
Purchase #7	$189.31	13.867%	$215.5616	$215.56	$215.55	$215.60
7 purchase totals =	$898.47		$978.1448	$978.15	$978.15	$978.20