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	$105.57	12.472%	$118.7367	$118.74	$118.75	$118.70
Purchase #2	$61.85	3.738%	$64.162	$64.16	$64.15	$64.20
Purchase #3	$174.94	12.146%	$196.1882	$196.19	$196.20	$196.20
Purchase #4	$241.36	3.427%	$249.6314	$249.63	$249.65	$249.60
Purchase #5	$99.69	4.256%	$103.9328	$103.93	$103.95	$103.90
Purchase #6	$103.38	13.463%	$117.298	$117.30	$117.30	$117.30
Purchase #7	$17.69	10.710%	$19.5846	$19.58	$19.60	$19.60
7 purchase totals =	$804.48		$869.5337	$869.53	$869.60	$869.50