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	$230.80	5.835%	$244.2672	$244.27	$244.25	$244.30
Purchase #2	$105.97	3.326%	$109.4946	$109.49	$109.50	$109.50
Purchase #3	$142.39	8.209%	$154.0788	$154.08	$154.10	$154.10
Purchase #4	$82.29	5.154%	$86.5312	$86.53	$86.55	$86.50
Purchase #5	$57.62	6.757%	$61.5134	$61.51	$61.50	$61.50
Purchase #6	$152.49	12.236%	$171.1487	$171.15	$171.15	$171.10
Purchase #7	$176.37	13.228%	$199.7002	$199.70	$199.70	$199.70
7 purchase totals =	$947.93		$1,026.7341	$1,026.73	$1,026.75	$1,026.70