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	$172.51	9.703%	$189.2486	$189.25	$189.25	$189.20
Purchase #2	$95.85	5.157%	$100.793	$100.79	$100.80	$100.80
Purchase #3	$197.99	6.537%	$210.9326	$210.93	$210.95	$210.90
Purchase #4	$71.40	10.860%	$79.154	$79.15	$79.15	$79.20
Purchase #5	$55.50	7.212%	$59.5027	$59.50	$59.50	$59.50
Purchase #6	$175.62	3.287%	$181.3926	$181.39	$181.40	$181.40
Purchase #7	$56.53	9.159%	$61.7076	$61.71	$61.70	$61.70
7 purchase totals =	$825.40		$882.7311	$882.72	$882.75	$882.70