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	$144.48	8.440%	$156.6741	$156.67	$156.65	$156.70
Purchase #2	$64.34	10.201%	$70.9033	$70.90	$70.90	$70.90
Purchase #3	$108.46	4.588%	$113.4361	$113.44	$113.45	$113.40
Purchase #4	$143.44	11.202%	$159.5081	$159.51	$159.50	$159.50
Purchase #5	$128.47	12.140%	$144.0663	$144.07	$144.05	$144.10
Purchase #6	$209.38	6.184%	$222.3281	$222.33	$222.35	$222.30
Purchase #7	$126.36	6.613%	$134.7162	$134.72	$134.70	$134.70
7 purchase totals =	$924.93		$1,001.6322	$1,001.64	$1,001.60	$1,001.60