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	$205.30	13.291%	$232.5864	$232.59	$232.60	$232.60
Purchase #2	$145.95	4.510%	$152.5323	$152.53	$152.55	$152.50
Purchase #3	$106.64	13.336%	$120.8615	$120.86	$120.85	$120.90
Purchase #4	$20.96	3.185%	$21.6276	$21.63	$21.65	$21.60
Purchase #5	$82.73	7.598%	$89.0158	$89.02	$89.00	$89.00
Purchase #6	$189.49	10.653%	$209.6764	$209.68	$209.70	$209.70
Purchase #7	$203.27	5.686%	$214.8279	$214.83	$214.85	$214.80
7 purchase totals =	$954.34		$1,041.1279	$1,041.14	$1,041.20	$1,041.10