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	$92.87	9.161%	$101.3778	$101.38	$101.40	$101.40
Purchase #2	$188.26	6.225%	$199.9792	$199.98	$200.00	$200.00
Purchase #3	$104.67	8.643%	$113.7166	$113.72	$113.70	$113.70
Purchase #4	$54.59	10.446%	$60.2925	$60.29	$60.30	$60.30
Purchase #5	$186.53	12.706%	$210.2305	$210.23	$210.25	$210.20
Purchase #6	$85.98	6.399%	$91.4819	$91.48	$91.50	$91.50
Purchase #7	$225.25	13.585%	$255.8502	$255.85	$255.85	$255.90
7 purchase totals =	$938.15		$1,032.9287	$1,032.93	$1,033.00	$1,033.00