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	$80.44	6.599%	$85.7482	$85.75	$85.75	$85.70
Purchase #2	$105.65	5.647%	$111.6161	$111.62	$111.60	$111.60
Purchase #3	$109.96	3.777%	$114.1132	$114.11	$114.10	$114.10
Purchase #4	$177.34	12.407%	$199.3426	$199.34	$199.35	$199.30
Purchase #5	$115.74	5.261%	$121.8291	$121.83	$121.85	$121.80
Purchase #6	$38.85	6.290%	$41.2937	$41.29	$41.30	$41.30
Purchase #7	$85.32	5.637%	$90.1295	$90.13	$90.15	$90.10
7 purchase totals =	$713.30		$764.0724	$764.07	$764.10	$763.90