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	$89.30	12.695%	$100.6366	$100.64	$100.65	$100.60
Purchase #2	$138.39	4.206%	$144.2107	$144.21	$144.20	$144.20
Purchase #3	$181.29	7.613%	$195.0916	$195.09	$195.10	$195.10
Purchase #4	$49.92	13.158%	$56.4885	$56.49	$56.50	$56.50
Purchase #5	$66.95	5.506%	$70.6363	$70.64	$70.65	$70.60
Purchase #6	$177.57	10.435%	$196.0994	$196.10	$196.10	$196.10
Purchase #7	$233.64	3.218%	$241.1585	$241.16	$241.15	$241.20
7 purchase totals =	$937.06		$1,004.3216	$1,004.33	$1,004.35	$1,004.30