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	$162.32	11.431%	$180.8748	$180.87	$180.85	$180.90
Purchase #2	$23.27	9.433%	$25.4651	$25.47	$25.45	$25.50
Purchase #3	$201.62	10.366%	$222.5199	$222.52	$222.50	$222.50
Purchase #4	$181.50	4.847%	$190.2973	$190.30	$190.30	$190.30
Purchase #5	$152.41	12.832%	$171.9673	$171.97	$171.95	$172.00
Purchase #6	$39.63	3.824%	$41.1455	$41.15	$41.15	$41.10
Purchase #7	$239.33	11.514%	$266.8865	$266.89	$266.90	$266.90
7 purchase totals =	$1,000.08		$1,099.1564	$1,099.17	$1,099.10	$1,099.20