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	$176.59	10.285%	$194.7523	$194.75	$194.75	$194.80
Purchase #2	$142.97	12.529%	$160.8827	$160.88	$160.90	$160.90
Purchase #3	$161.59	12.186%	$181.2814	$181.28	$181.30	$181.30
Purchase #4	$98.39	9.574%	$107.8099	$107.81	$107.80	$107.80
Purchase #5	$86.42	4.105%	$89.9675	$89.97	$89.95	$90.00
Purchase #6	$105.97	6.322%	$112.6694	$112.67	$112.65	$112.70
Purchase #7	$239.79	5.743%	$253.5611	$253.56	$253.55	$253.60
7 purchase totals =	$1,011.72		$1,100.9243	$1,100.92	$1,100.90	$1,101.10