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	$203.70	6.666%	$217.2786	$217.28	$217.30	$217.30
Purchase #2	$188.62	11.333%	$209.9963	$210.00	$210.00	$210.00
Purchase #3	$154.27	4.147%	$160.6676	$160.67	$160.65	$160.70
Purchase #4	$200.40	7.637%	$215.7045	$215.70	$215.70	$215.70
Purchase #5	$65.59	10.176%	$72.2644	$72.26	$72.25	$72.30
Purchase #6	$142.38	5.453%	$150.144	$150.14	$150.15	$150.10
Purchase #7	$45.52	11.247%	$50.6396	$50.64	$50.65	$50.60
7 purchase totals =	$1,000.48		$1,076.6950	$1,076.69	$1,076.70	$1,076.70