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	$81.77	12.524%	$92.0109	$92.01	$92.00	$92.00
Purchase #2	$204.56	12.871%	$230.8889	$230.89	$230.90	$230.90
Purchase #3	$41.74	10.693%	$46.2033	$46.20	$46.20	$46.20
Purchase #4	$19.25	5.679%	$20.3432	$20.34	$20.35	$20.30
Purchase #5	$121.26	8.617%	$131.709	$131.71	$131.70	$131.70
Purchase #6	$105.62	5.311%	$111.2295	$111.23	$111.25	$111.20
Purchase #7	$54.94	11.160%	$61.0713	$61.07	$61.05	$61.10
7 purchase totals =	$629.14		$693.4561	$693.45	$693.45	$693.40