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	$145.57	13.568%	$165.3209	$165.32	$165.30	$165.30
Purchase #2	$43.58	6.256%	$46.3064	$46.31	$46.30	$46.30
Purchase #3	$93.64	7.470%	$100.6349	$100.63	$100.65	$100.60
Purchase #4	$179.85	3.761%	$186.6142	$186.61	$186.60	$186.60
Purchase #5	$168.58	10.866%	$186.8979	$186.90	$186.90	$186.90
Purchase #6	$211.40	6.474%	$225.086	$225.09	$225.10	$225.10
Purchase #7	$208.87	5.685%	$220.7443	$220.74	$220.75	$220.70
7 purchase totals =	$1,051.49		$1,131.6046	$1,131.60	$1,131.60	$1,131.50